Each morning for the past two days I’ve noticed that HomeKit stops responding and requires a restart of openHAB. Any ideas about what might be causing this?
Is there a way to enable debug logging for HomeKit?
Still happening, every day, even sometimes multiple times per day.
I have the same problem…also no answer yet 
You can enable debug logging, even in a separate file to make it more visible. BUT: for me it doesnt help, because it just stops. I “terminates” the conection and thats it. Then it continues “publishing changes” but looking into Homekit APP just informs that OH is not available
in the console
ssh openhab@localhost -p 8101
PW: habopen
you can set the log level for the bundle, and you can restart the bundle (bundle:list note the Homekit number and do a bundle:restart NUMBER) so at least you dont need to restart the whole OH2 server
But at the end of the day, it is no cure 
PS:
I hope you fixed it in the meantime 
the same issue started happening to me, running OH3. i could not figure the reason for it. nothing in the logs about Homekit.
is anyone experiencing this? and possibly found the root cause ?
Me too! At first i thought it has something to do with the null-state of the item but my homekit does not respond either after some time.
Also using OH3.
Maybe same problem:
Same here. Worked until OH3M4 I think.