Upload Stuck (for 60sec)

Just recently I've upgraded SmartFTP Pro from V4 to the latest version and since then I experience problems during file upload and Directory browsing.
Most of the time file upload is stuck for exactly a minute. I have the same issue with directory browsing, just not that frequently.
It looks like the first transfer attempt times out (after 60s) and only after this the 2nd attempt succeeds.
 
Here's what the upload log Looks like:
 
[08:04:31] Operation begin
[08:04:31] Getting properties (Size, Date modified) of "W:\Web\www.losv.li-13\Portals\0\Skins\losv\swSkin.css"
[08:04:31] CWD /web/www.losv.li-13/Portals/0/Skins
[08:04:31] 250 CWD successful. "/web/www.losv.li-13/Portals/0/Skins" is current directory.
[08:04:31] PWD
[08:04:31] 257 "/web/www.losv.li-13/Portals/0/Skins" is current directory.
[08:04:31] MLST losv
[08:04:31] 250-Listing /web/www.losv.li-13/Portals/0/Skins/losv
[08:04:31]  type=dir;modify=20140304132746; /web/www.losv.li-13/Portals/0/Skins/losv
[08:04:31] 250 End
[08:04:31] CWD /web/www.losv.li-13/Portals/0/Skins/losv
[08:04:31] 250 CWD successful. "/web/www.losv.li-13/Portals/0/Skins/losv" is current directory.
[08:04:31] PWD
[08:04:31] 257 "/web/www.losv.li-13/Portals/0/Skins/losv" is current directory.
[08:04:31] PASV
[08:04:31] 227 Entering Passive Mode (10,0,0,18,229,205)
[08:04:31] Opening data connection to 10.0.0.18 Port: 58829
[08:04:31] STOR swSkin.css
[08:04:31] 150 Connection accepted
[08:04:31] 40864 bytes transferred. (1.69 MB/s) (23 ms)
[08:05:31] Timeout (60s).
[08:05:31] Active Help: https://www.smartftp.com/support/kb/74
[08:05:31] Client closed the connection.
[08:05:31] Transfer failed.
[08:05:31] Operation end
[08:05:31] Unknown error 0x80043103
[08:05:31] Operation begin
[08:05:31] Getting properties (Size, Date modified) of "W:\Web\www.losv.li-13\Portals\0\Skins\losv\swSkin.css"
[08:05:31] Resolving host name "10.0.0.18"
[08:05:31] Connecting to 10.0.0.18 Port: 21
[08:05:31] Connected to 10.0.0.18.
[08:05:31] 220-FileZilla Server version 0.9.40 beta
[08:05:31] 220-written by Tim Kosse (Tim.Kosse@gmx.de)
[08:05:31] 220 Please visit
[08:05:31] USER georgi.latev
[08:05:31] 331 Password required for georgi.latev
[08:05:31] PASS (hidden)
[08:05:31] 230 Logged on
[08:05:31] SYST
[08:05:31] 215 UNIX emulated by FileZilla
[08:05:31] Detected Server Type: UNIX
[08:05:31] RTT: 10.044 ms
[08:05:31] FEAT
[08:05:31] 211-Features:
[08:05:31]  MDTM
[08:05:31]  REST STREAM
[08:05:31]  SIZE
[08:05:31]  MLST type*;size*;modify*;
[08:05:31]  MLSD
[08:05:31]  UTF8
[08:05:31]  CLNT
[08:05:31]  MFMT
[08:05:31] 211 End
[08:05:31] CLNT SmartFTP 6.0.2016.0
[08:05:31] 200 Don't care
[08:05:31] OPTS UTF8 ON
[08:05:31] 200 UTF8 mode enabled
[08:05:31] Detected Server Software: FileZilla Server
[08:05:31] PWD
[08:05:31] 257 "/" is current directory.
[08:05:31] CWD /web/www.losv.li-13/Portals/0/Skins
[08:05:31] 250 CWD successful. "/web/www.losv.li-13/Portals/0/Skins" is current directory.
[08:05:31] PWD
[08:05:31] 257 "/web/www.losv.li-13/Portals/0/Skins" is current directory.
[08:05:31] MLST losv
[08:05:31] 250-Listing /web/www.losv.li-13/Portals/0/Skins/losv
[08:05:31]  type=dir;modify=20140304132746; /web/www.losv.li-13/Portals/0/Skins/losv
[08:05:31] 250 End
[08:05:31] Getting properties (Size) of "/web/www.losv.li-13/Portals/0/Skins/losv/swSkin.css"
[08:05:31] CWD /web/www.losv.li-13/Portals/0/Skins/losv
[08:05:31] 250 CWD successful. "/web/www.losv.li-13/Portals/0/Skins/losv" is current directory.
[08:05:31] PWD
[08:05:31] 257 "/web/www.losv.li-13/Portals/0/Skins/losv" is current directory.
[08:05:31] MLST swSkin.css
[08:05:31] 250-Listing /web/www.losv.li-13/Portals/0/Skins/losv/swSkin.css
[08:05:31]  type=file;size=40864;modify=20140512080618; /web/www.losv.li-13/Portals/0/Skins/losv/swSkin.css
[08:05:31] 250 End
[08:05:31] Skipping transfer for file "W:\Web\www.losv.li-13\Portals\0\Skins\losv\swSkin.css". Reason: File size is equal.
[08:05:31] Getting properties (Date modified) of "W:\Web\www.losv.li-13\Portals\0\Skins\losv\swSkin.css"
[08:05:31] Using cached properties
[08:05:31] Setting properties (Date modified) of "/web/www.losv.li-13/Portals/0/Skins/losv/swSkin.css"
[08:05:31] MFMT 20140512080357 swSkin.css
[08:05:31] 213 modify=20140512080357; /web/www.losv.li-13/Portals/0/Skins/losv/swSkin.css
[08:05:31] MLST swSkin.css
[08:05:31] 250-Listing /web/www.losv.li-13/Portals/0/Skins/losv/swSkin.css
[08:05:31]  type=file;size=40864;modify=20140512080357; /web/www.losv.li-13/Portals/0/Skins/losv/swSkin.css
[08:05:31] 250 End
[08:05:31] Getting properties (Size) of "W:\Web\www.losv.li-13\Portals\0\Skins\losv\swSkin.css"
[08:05:31] Using cached properties
[08:05:31] Getting properties (Size) of "/web/www.losv.li-13/Portals/0/Skins/losv/swSkin.css"
[08:05:31] Using cached properties
[08:05:31] Source File Size=40864, Destination file size=40864
[08:05:31] Operation end
 

The problem seems to be that SmartFTP waits for the transfer complete reply from the server but it never receives it.
[08:04:31] STOR swSkin.css
[08:04:31] 150 Connection accepted
[08:04:31] 40864 bytes transferred. (1.69 MB/s) (23 ms)
[08:05:31] Timeout (60s).
There are many reasons why this may happen. I would first try to reproduce it on a fresh installation of Windows 8.1.

First of all thx for the reply
 
It seems that this entry is false as it states that all data has already been transferred the same second the operation started. I uploaded a bigger file (3+mb file which usually takes around 10 seconds to upload) and received the same log statements:
 
[11:15:59] Operation begin
[11:15:59] Getting properties (Size, Date modified) of "C:\Users\user.user\Desktop\LAFV\2014_LAFV_FL_bergwelt_02.jpg"
[11:15:59] CWD /web/www.lafv.li/Portals/0/Skins/lafv/media
[11:15:59] 250 CWD successful. "/web/www.lafv.li/Portals/0/Skins/lafv/media" is current directory.
[11:15:59] PWD
[11:15:59] 257 "/web/www.lafv.li/Portals/0/Skins/lafv/media" is current directory.
[11:15:59] MLST bg
[11:15:59] 250-Listing /web/www.lafv.li/Portals/0/Skins/lafv/media/bg
[11:15:59]  type=dir;modify=20140515111607; /web/www.lafv.li/Portals/0/Skins/lafv/media/bg
[11:15:59] 250 End
[11:15:59] CWD /web/www.lafv.li/Portals/0/Skins/lafv/media/bg
[11:15:59] 250 CWD successful. "/web/www.lafv.li/Portals/0/Skins/lafv/media/bg" is current directory.
[11:15:59] PWD
[11:15:59] 257 "/web/www.lafv.li/Portals/0/Skins/lafv/media/bg" is current directory.
[11:15:59] PASV
[11:15:59] 227 Entering Passive Mode (10,0,0,18,218,115)
[11:15:59] Opening data connection to 10.0.0.18 Port: 55923
[11:15:59] STOR 2014_LAFV_FL_bergwelt_02.jpg
[11:15:59] 150 Connection accepted
[11:15:59] 3236288 bytes transferred. (205 MB/s) (15 ms)
[11:16:59] Timeout (60s).
[11:16:59] Active Help: https://www.smartftp.com/support/kb/74
[11:16:59] Client closed the connection.
[11:16:59] Transfer failed.
[11:16:59] Operation end
[11:16:59] Unknown error 0x80043103
[11:16:59] Operation begin
[11:16:59] Getting properties (Size, Date modified) of "C:\Users\user.user\Desktop\LAFV\2014_LAFV_FL_bergwelt_02.jpg"
[11:16:59] Resolving host name "10.0.0.18"
[11:16:59] Connecting to 10.0.0.18 Port: 21
[11:16:59] Connected to 10.0.0.18.
[11:16:59] 220-FileZilla Server version 0.9.40 beta
[11:16:59] 220-written by Tim Kosse (Tim.Kosse@gmx.de)
[11:16:59] 220 Please visit
[11:16:59] USER user.user
[11:16:59] 331 Password required for user.user
[11:16:59] PASS (hidden)
[11:16:59] 230 Logged on
[11:16:59] SYST
[11:16:59] 215 UNIX emulated by FileZilla
[11:16:59] Detected Server Type: UNIX
[11:16:59] RTT: 9.536 ms
[11:16:59] FEAT
[11:16:59] 211-Features:
[11:16:59]  MDTM
[11:16:59]  REST STREAM
[11:16:59]  SIZE
[11:16:59]  MLST type*;size*;modify*;
[11:16:59]  MLSD
[11:16:59]  UTF8
[11:16:59]  CLNT
[11:16:59]  MFMT
[11:16:59] 211 End
[11:16:59] CLNT SmartFTP 6.0.2016.0
[11:16:59] 200 Don't care
[11:16:59] OPTS UTF8 ON
[11:16:59] 200 UTF8 mode enabled
[11:16:59] Detected Server Software: FileZilla Server
[11:16:59] PWD
[11:16:59] 257 "/" is current directory.
[11:16:59] CWD /web/www.lafv.li/Portals/0/Skins/lafv/media
[11:16:59] 250 CWD successful. "/web/www.lafv.li/Portals/0/Skins/lafv/media" is current directory.
[11:16:59] PWD
[11:16:59] 257 "/web/www.lafv.li/Portals/0/Skins/lafv/media" is current directory.
[11:16:59] MLST bg
[11:16:59] 250-Listing /web/www.lafv.li/Portals/0/Skins/lafv/media/bg
[11:16:59]  type=dir;modify=20140515111607; /web/www.lafv.li/Portals/0/Skins/lafv/media/bg
[11:16:59] 250 End
[11:16:59] Getting properties (Size) of "/web/www.lafv.li/Portals/0/Skins/lafv/media/ ... .jpg"</div>
[11:16:59] CWD /web/www.lafv.li/Portals/0/Skins/lafv/media/bg
[11:16:59] 250 CWD successful. "/web/www.lafv.li/Portals/0/Skins/lafv/media/bg" is current directory.
[11:16:59] PWD
[11:16:59] 257 "/web/www.lafv.li/Portals/0/Skins/lafv/media/bg" is current directory.
[11:16:59] MLST 2014_LAFV_FL_bergwelt_02.jpg
[11:16:59] 250-Listing /web/www.lafv.li/Portals/0/Skins/lafv/media/ ... 2.jpg</div>
[11:16:59]  type=file;size=3236288;modify=20140515111752; /web/www.lafv.li/Portals/0/Skins/lafv/media/ ... 2.jpg</div>
[11:16:59] 250 End
[11:16:59] Skipping transfer for file "C:\Users\user.user\Desktop\LAFV\2014_LAFV_FL_bergwelt_02.jpg". Reason: File size is equal.
[11:16:59] Getting properties (Date modified) of "C:\Users\user.user\Desktop\LAFV\2014_LAFV_FL_bergwelt_02.jpg"
[11:16:59] Using cached properties
[11:16:59] Setting properties (Date modified) of "/web/www.lafv.li/Portals/0/Skins/lafv/media/ ... .jpg"</div>
[11:16:59] MFMT 20140408134112 2014_LAFV_FL_bergwelt_02.jpg
[11:16:59] 213 modify=20140408134112; /web/www.lafv.li/Portals/0/Skins/lafv/media/ ... 2.jpg</div>
[11:16:59] MLST 2014_LAFV_FL_bergwelt_02.jpg
[11:16:59] 250-Listing /web/www.lafv.li/Portals/0/Skins/lafv/media/ ... 2.jpg</div>
[11:16:59]  type=file;size=3236288;modify=20140408134112; /web/www.lafv.li/Portals/0/Skins/lafv/media/ ... 2.jpg</div>
[11:16:59] 250 End
[11:16:59] Getting properties (Size) of "C:\Users\user.user\Desktop\LAFV\2014_LAFV_FL_bergwelt_02.jpg"
[11:16:59] Using cached properties
[11:16:59] Getting properties (Size) of "/web/www.lafv.li/Portals/0/Skins/lafv/media/ ... .jpg"</div>
[11:16:59] Using cached properties
[11:16:59] Source File Size=3236288, Destination file size=3236288
[11:16:59] Operation end