Freenas hangs after restoring timemachine permissions and starting timemachine backup

My timemachine backups stopped working after the upgrade to 11.1 or 11.2
I have tried to revive them which is probably related to the permission of the AFP share (all permissions were gone, might be related to a migration issue).
When I restored the permission and started timemachine, freenas hangs and I could only get access to it by resetting it through ipmi (UI and ssh were not responsive any more).

In the ipmi console I see the error message: swap_pager_getswapspace(xx): failed
In middlewared.log I see the following error around the time of the issue.

[2019/12/10 08:59:29] (DEBUG) ServiceService._simplecmd():281 - Calling: reload(afp)
[2019/12/10 09:00:41] (WARNING) middlewared._loop_monitor_thread():1203 - Task seems blocked:
File "/usr/local/lib/python3.6/site-packages/middlewared/main.py", line 1271, in run
self.__loop.run_forever()
File "/usr/local/lib/python3.6/asyncio/base_events.py", line 438, in run_forever
self._run_once()
File "/usr/local/lib/python3.6/asyncio/base_events.py", line 1451, in _run_once
handle._run()
File "/usr/local/lib/python3.6/asyncio/events.py", line 145, in _run
self._callback(*self._args)
File "/usr/local/lib/python3.6/site-packages/middlewared/main.py", line 165, in call_method
result = await self.middleware.call_method(self, message)
File "/usr/local/lib/python3.6/site-packages/middlewared/main.py", line 1096, in call_method
return await self._call(message ['method'] , serviceobj, methodobj, params, app=app, io_thread=False)
File "/usr/local/lib/python3.6/site-packages/middlewared/main.py", line 1044, in _call
return await methodobj(*args)
File "/usr/local/lib/python3.6/site-packages/middlewared/schema.py", line 664, in nf
return await f(*args, **kwargs)
File "/usr/local/lib/python3.6/site-packages/middlewared/service.py", line 201, in config
return await self._get_or_insert(self._config.datastore, options)
File "/usr/local/lib/python3.6/site-packages/middlewared/service.py", line 211, in _get_or_insert
return await self.middleware.call('datastore.config', datastore, options)

[2019/12/10 09:00:43] (WARNING) middlewared._loop_monitor_thread():1203 - Task seems blocked:
File "/usr/local/lib/python3.6/site-packages/middlewared/main.py", line 1271, in run
self.__loop.run_forever()
File "/usr/local/lib/python3.6/asyncio/base_events.py", line 438, in run_forever
self._run_once()
File "/usr/local/lib/python3.6/asyncio/base_events.py", line 1451, in _run_once
handle._run()
File "/usr/local/lib/python3.6/asyncio/events.py", line 145, in _run
self._callback(*self._args)
File "/usr/local/lib/python3.6/site-packages/middlewared/main.py", line 165, in call_method
result = await self.middleware.call_method(self, message)
File "/usr/local/lib/python3.6/site-packages/middlewared/main.py", line 1096, in call_method
return await self._call(message ['method'] , serviceobj, methodobj, params, app=app, io_thread=False)
File "/usr/local/lib/python3.6/site-packages/middlewared/main.py", line 1044, in _call
return await methodobj(*args)
File "/usr/local/lib/python3.6/site-packages/middlewared/schema.py", line 664, in nf
return await f(*args, **kwargs)
File "/usr/local/lib/python3.6/site-packages/middlewared/service.py", line 201, in config
return await self._get_or_insert(self._config.datastore, options)
File "/usr/local/lib/python3.6/site-packages/middlewared/service.py", line 211, in _get_or_insert
return await self.middleware.call('datastore.config', datastore, options)

[2019/12/10 09:01:03] (WARNING) middlewared._loop_monitor_thread():1200 - run_in_thread seems to be blocking event loop
[2019/12/10 09:01:05] (WARNING) middlewared._loop_monitor_thread():1200 - run_in_thread seems to be blocking event loop
[2019/12/10 09:01:07] (WARNING) middlewared._loop_monitor_thread():1200 - run_in_thread seems to be blocking event loop