Upload often fails due to libcurl error

I use Seafile to backup my .thunderbird folder manually using the GUI client on Archlinux (current version 9.0.8). The sync often fails by stopping at half-way, with no error message on the GUI. In the logs I see:

[08/27/24 09:21:50] sync-mgr.c(604): Repo '.thunderbird' sync state transition from 'synchronized' to 'committing'.
[08/27/24 09:21:50] repo-mgr.c(1806): Failed to stat /home/mori/.thunderbird/jl5nbx4z.default/lock: No such file or directory.
[08/27/24 09:22:26] sync-mgr.c(604): Repo '.thunderbird' sync state transition from 'committing' to 'uploading'.
[08/27/24 09:22:26] http-tx-mgr.c(1169): Transfer repo 'd5f29533': ('normal', 'init') --> ('normal', 'check')
[08/27/24 09:22:26] http-tx-mgr.c(1169): Transfer repo 'd5f29533': ('normal', 'check') --> ('normal', 'commit')
[08/27/24 09:22:26] http-tx-mgr.c(1169): Transfer repo 'd5f29533': ('normal', 'commit') --> ('normal', 'fs')
[08/27/24 09:22:27] http-tx-mgr.c(1169): Transfer repo 'd5f29533': ('normal', 'fs') --> ('normal', 'data')
[08/27/24 09:23:10] http-tx-mgr.c(943): libcurl failed to PUT https://basket.fi.infn.it/seafhttp/repo/d5f29533-2819-4a45-a71d-56bf2de2daa8/block/6e1779c2915246436612abf6154124e1164cff99: Failed to open/read local data from file/application.
[08/27/24 09:23:10] http-tx-mgr.c(943): libcurl failed to PUT https://basket.fi.infn.it/seafhttp/repo/d5f29533-2819-4a45-a71d-56bf2de2daa8/block/23f1e9b732ed67ca8992fecef3f5820da14abe3f: Operation was aborted by an application callback.
[08/27/24 09:23:11] http-tx-mgr.c(943): libcurl failed to PUT https://basket.fi.infn.it/seafhttp/repo/d5f29533-2819-4a45-a71d-56bf2de2daa8/block/3829b637b48f9ca4a6d0ef9c1f2647892dc229bb: Operation was aborted by an application callback.
[08/27/24 09:23:12] http-tx-mgr.c(1169): Transfer repo 'd5f29533': ('normal', 'data') --> ('error', 'finished')
[08/27/24 09:23:12] sync-mgr.c(642): Repo '.thunderbird' sync state transition from uploading to 'error': 'Network error'.

It happens both with Thunderbird running and not running. Repeating the sync, possibly multiple times, the transfer ends successfully.
I don’t understand whether it is a problem on the client side (as the Failed to open/read local data from file/application. message suggests) or on the server side (currently on version 6.0.7, I already asked my IT department to upgrade), so any help is welcome.

Hi,
this could be a server side issue, you can wait to upgrade the version of the server and see if there is an issue. Also the files on the client side are uploaded in chunks, make sure your local firewall doesn’t intercept such requests.

Thanks for your help. I’ll wait the server upgrade and eventually post again if it will not fix. I don’t think it’s a firewall problem, otherwise it would not be random, I guess.