File sync stalls for 60 seconds on about 10% of the files

[ds00424]

FYI, Nothing has changed in the setup (Client or Server) other than upgrading to BestSync2019 (from 2013). I have ensured BestSync2019 is in the Widows Firewall as an allowed application. There are no restrictions on sending ports in the windows firewall or the network hardware router (dd-wrt).

I just uploaded 7 files. The first 3 went quickly. Each of the next 4 took minutes to complete. I think it took 1 min to get thru the upload and then another min to get thru the verify -- for each of the remaining 4 files. Very painful.

I have attached a screen shot when it was "stalled".
And below is the output from the last synced file. But unfortunately, there are no timestamps to show the timing

Is there any debugging I can turn on to get more info as to what is happening behind the scenes?

========
/hosteddb/version
>PASV
<227 Entering Passive Mode (173,247,240,143,127,210)
>RETR version
<150 Accepted data connection
<226-File successfully transferred
<226 0.001 seconds (measured here), 28.53 Kbytes per second
>PASV
<227 Entering Passive Mode (173,247,240,143,122,231)
>RETR version
<150 Accepted data connection
<226-File successfully transferred
<226 0.000 seconds (measured here), 0.93 Mbytes per second
/hosteddb/_BS8_EXVCBUN2CHLAC_2B_0C_00_MD5_2AF72F100C356273D46284F6FD1DFC08_OZSXE43JN5XA.BS_
>PASV
<227 Entering Passive Mode (173,247,240,143,135,70)
>STOR _BS8_EXVCBUN2CHLAC_2B_0C_00_MD5_2AF72F100C356273D46284F6FD1DFC08_OZSXE43JN5XA.BS_
<150 Accepted data connection
<226-File successfully transferred
<226 0.067 seconds (measured here), 0.63 Kbytes per second
>MFMT 20200413174152 _BS8_EXVCBUN2CHLAC_2B_0C_00_MD5_2AF72F100C356273D46284F6FD1DFC08_OZSXE43JN5XA.BS_
<213 UTIME OK
>PASV
<227 Entering Passive Mode (173,247,240,143,120,154)
>RETR _BS8_EXVCBUN2CHLAC_2B_0C_00_MD5_2AF72F100C356273D46284F6FD1DFC08_OZSXE43JN5XA.BS_
<150 Accepted data connection
<226-File successfully transferred
<226 0.000 seconds (measured here), 0.66 Mbytes per second
/hosteddb/version
>DELE version
<250 Deleted version
>RNFR _BS8_EXVCBUN2CHLAC_2B_0C_00_MD5_2AF72F100C356273D46284F6FD1DFC08_OZSXE43JN5XA.BS_
<350 RNFR accepted - file exists, ready for destination
>RNTO version
<250 File successfully renamed or moved
========

[ds00424]

A little more info.
I tried BS2020 15.0.1.1. it is the portable version (if that matters) and has an ultimate license
I synced 20 files from a Network share to an FTP folder.
The FTP folder was empty so all 20 files needed to be uploaded.

16 files got uploaded quickly (a few seconds), 3 files said "Processing..." and stayed that way for about a minute and then were uploaded, 1 file said "Failed: The connection has been broken due to keep-alive activity detecting a failure while the operation was in progress." -- After about 2 minutes that file was uploaded successfully.

Not sure if this helps.
Again would be great if I could turn on some debug flag that would print out more debugging info to understand why the stalls.

One other observation: in the preview window prior to syncing, when I right click and select "View Difference" -- sometimes it takes a minute or so to show the file diff. I assume this is related.

Thanks.

[ds00424]

Some more info:
I set the BS task to process 1 file at a time. On the server side I did "tail -f | grep pure-ftpd"
I started the task and the preview analyzed the fiels and showed the 20 files that needed to be uploaded (target folder was empty).
I clicked start and 1 file uploaded quickly and then the second stalled. I let it sit for about 10 seconds and than grabbed the tail output.

Here is the tail output: (Ip addresses, server names and user names changed to protect the innocent).
====
Apr 16 11:23:33 vps00000 pure-ftpd: (?@XX.XX.XX.XX) [INFO] New connection from XX.XX.XX.XX
Apr 16 11:23:33 vps00000 pure-ftpd: (?@XX.XX.XX.XX) [INFO] ftpserver@example.com is now logged in
Apr 16 11:23:43 vps00000 pure-ftpd: (ftpserver@example.com@XX.XX.XX.XX) [INFO] Logout.
Apr 16 11:23:43 vps00000 pure-ftpd: (?@XX.XX.XX.XX) [INFO] New connection from XX.XX.XX.XX
Apr 16 11:23:43 vps00000 pure-ftpd: (?@XX.XX.XX.XX) [INFO] ftpserver@example.com is now logged in
Apr 16 11:23:44 vps00000 pure-ftpd: (ftpserver@example.com@XX.XX.XX.XX) [NOTICE] Restarting at 577
Apr 16 11:23:44 vps00000 pure-ftpd: (ftpserver@example.com@XX.XX.XX.XX) [NOTICE] /home/ftpuser/public_html//test/sync/include/_BS8_BPJ73TYEBLLAC_0241_06_00_MD5_07F861ADA72D5206B4EBF04F1768A2B5_MFBW63TGNFTS44DIOA.BS_.php uploaded (0 bytes, 0.00KB/sec)
Apr 16 11:23:45 vps00000 pure-ftpd: (ftpserver@example.com@XX.XX.XX.XX) [NOTICE] /home/ftpuser/public_html//test/sync/include/_BS8_BPJ73TYEBLLAC_0241_06_00_MD5_07F861ADA72D5206B4EBF04F1768A2B5_MFBW63TGNFTS44DIOA.BS_.php downloaded (577 bytes, 4580.22KB/sec)
Apr 16 11:23:45 vps00000 pure-ftpd: (ftpserver@example.com@XX.XX.XX.XX) [NOTICE] File successfully renamed or moved: [_BS8_BPJ73TYEBLLAC_0241_06_00_MD5_07F861ADA72D5206B4EBF04F1768A2B5_MFBW63TGNFTS44DIOA.BS_.php]->[aConfig.php]
Apr 16 11:23:45 vps00000 pure-ftpd: (ftpserver@example.com@XX.XX.XX.XX) [INFO] Can't change directory to /test/sync/WebSvcs: No such file or directory
Apr 16 11:23:46 vps00000 pure-ftpd: (ftpserver@example.com@XX.XX.XX.XX) [NOTICE] /home/ftpuser/public_html//test/sync/WebSvcs/_BS8_GCUQIDUQBTLAC_0538_06_00_MD5_16A7FC122BF963099E25D2D8EB7AFDA6_MNXXK3TUNFSXGLTQNBYA.BS_.php uploaded (1336 bytes, 16.76KB/sec)
Apr 16 11:23:46 vps00000 pure-ftpd: (ftpserver@example.com@XX.XX.XX.XX) [NOTICE] /home/ftpuser/public_html//test/sync/WebSvcs/_BS8_GCUQIDUQBTLAC_0538_06_00_MD5_16A7FC122BF963099E25D2D8EB7AFDA6_MNXXK3TUNFSXGLTQNBYA.BS_.php downloaded (1336 bytes, 24213.52KB/sec)
====

So looks like BestSync was stalled after the second file was uploaded and then downloaded, but not yet renamed. You're the expert, but this implies to me that Best Sync was performing the verification of original file to uploaded file and for some reason is getting stuck for some time during this process. I don't see that this is related to firewall or the ftp server.

Thanks.
David

[ds00424]

I disabled the verify in BestSync and none of the 20 files stalled. I repeated the test 3 times.
Something in the verify process is causing the stall.

At least I have a workaround, but would really like to have the verify working.

Thanks.