Problem..

[simoncn]

The crash log you posted is saying you had downloaded and installed the wrong MinimServer file for your NAS. This isn't relevant to the current problems.

When you next get the problem (and before restarting MinimServer), use Synology File Station to look at the minimserver.log file in the MinimServer/appData folder. Are there any error messages near the end of this file?

If you don't see any errors in the log file, you can select 'Show log' from MinimWatch and change the logging level from Info to Debug. This will produce more output in the minimserver.log file and the additional output might provide some clues.