Sudenly not able to connect to GUI

Dear all,

I’m not sure if this is the right forum section.
I’m having the following issue:

Yesterday, I installed 2025-12 and then continued working with HA as usual.
Suddenly this afternoon, out of nowhere, the GUI became inaccessible.
The host is an INTEL NUC and everything seemed fine on the connected display, ‘standard HA CLI screen’, and I was able to execute commands via the CLI.

I reset the host via the CLI and restarted HA. The boot process runs without error and ends in the familiar CLI screen with connection info.
Unfortunately, this had no effect; the GUI URL gives a connection error. (Ping to the IP works.)
Sometimes, if I was very quick, the login screen appeared, but then it was over.

After many attempts via the CLI, I got HA into safe mode.
Each time, there was a message saying that another job was active.
Now I can access the GUI again with all the limitations of safe mode.
But no matter where I look in the log files, there is no clue as to what the problem could be.
I didn’t make any updates or changes today.

I can set all the add-ons to disabled while in safe mode, then restart and activate them one by one, with the chance that I’ll get stuck again.

I’m open to any ideas to get it working again.
Does anyone have any ideas on how to proceed??

did you see Homeassistant stopped working : also backup doesn't look to work - #9 by rnest?