HomeAssistant frontend no longer loading


I had two HomeAssistant systems running here and a Pi3. Both systems (one as a backup and to test stuff) run stable for a few months now. No issues whatsoever. One system uses a SSD and the other an normal SD card.

Yesterday, suddenly both systems crashed. I could not enter the interface of both of the systems. Up in till early in the evening, when I was not at home, it was running ok.

So, I formatted the SSD, installed raspbian, docker and re-installed HomeAssistant supervisor version. Works fine. As soon as I restore my backup from 2 days ago, the system go’s down again. Same for a backup from a week ago.

The backup system SD card is flashed with the HomeAssistant’s latest image. Also runs fine, until I restore my backup. As soon as I do that, the system crashes again. Same for the one week old backup.

So, when I check the supervisor log’s I see this error passing by:

ERROR (MainThread) [supervisor.homeassistant.api] Error on call

I suspect the error above is the reason I can not access the interface, as I noticed that my MQTT server is running, because I can see all the sensor data pass by in a MQTT explorer. I can also access the disk using the SMB add-on and see the config, etc. etc.
Also, looking at the way the lights on my pi flash on harddisk activity, I get the feeling it’s in a boot loop. The lights flash the same every few seconds.

So, is the error above the reason I can not access my user interface anymore? I tried a docker repair using the supervisor tools. That did not help. Are there any other options I can try?