I opened this issue cron rules stop working every few days · Issue #4130 · eclipse-archived/smarthome · GitHub
I copied all my rules to a test machine and found out that the copied also stop working but not half as often. There is no z-wave traffic on my trst machine. I am still working on removing all my specific stuff from the copied rules in order to post them.
Meanwhile I also found out that while I was heavily increasing http traffic within my original rules, time between two breakdowns was decreasing. The next thing I wanna do is to remove http binding and put all this stuff into shell scripts that can be called by exec binding. Maybe this helps identifying the problem.