Instable Openhab

I have a problem with my openhab installation: it is unstable. Last night it suddenly stopped all timers. There a no rules executed, no calenders updated etc.
If I restart openhab I have the problem that I often get “channel not found for datapoint” errors for my homematic devices. So I normally have to do 5-7 restarts until everything is working. Also some of the devices don’t send any values and I cannot send any command to them (there is no error message).
Besides this behaviour there are not errors displayed in openhab log. So how can I debug the system? It is very uncomfortable to start the system 2-3 times a week which costs me a lot of time because of the channel not found.
Version: openHAB 2.3.0 Release Build
Homegear: 0.7.30-1900
HM-CFG-USB stick for HM devices

Thanks for any help on how to debug!

You can start by looking in the log files and if that doesn’t help increase log levels to DEBUG or TRACE mode: See:

You can change and monitor log levels via the console:

This should give you a start.

Thanks @hilbrand, I just set the org.openhab level to DEBUG. Maybe I find something. Today the whole system stoped at one point (before I enabled DEBUG) and nothing has been added to the log.