Random delay while working

Hello board,
I’m facing random delays and stucks while I’m working with the board. I was neither be able to narrow it down to a specific action nor to reproduce the issue. There are certain actions which tend to be more affected than others, but at the end it’s a little bit curious. Even because the problems can occur at the same time at person A, and person B, which is doing the same things in the same project, is not affected.
When the problem occurs I see the spin-wheel turning round and round. I can reload the page and everything was saved and I can work normally again. When I don’t reload the page, it tooks about 32 seconds and then the change is saved and the page is back again.

I’ve tested quite a lot. I seems that the webpage request is not closed correctly. Why? I found out that at the same time when the problem occurs there is an open database session (seen in ‘show processlist;’ - I’m using MySQL from the beginning). Normally when I work with kanboard the database connection is closed after milliseconds. But when the problem comes up the db connections remains open. Then after round about 32 seconds (varies between 31-34) the db connection is closed and the site is back again. So there seems to be some kind of timeout.

I’ve looked at several possible causes:

  • Firewall: the kanboad is reachable behind a firewall. I’ve tested with a client in the same network segment with no difference
  • HTTP/HTTPS: both protocols are affected
  • HW/SW limitations: the software is running on a virtual machine (VMware) with 4 vCPU, 4 GB RAM, debian 10 - VMware and virtual machine are idle enough
  • Client problems: tested with different browers and different client PCs

Is there anybody out there facing the same problems? At the end I’m running out of ideas where to search furthermore.