Pressure changed overnight? (to high) Anybody has any idea what can make the pressure go up overnight?

From the normal 7,5, its now over 12 BAR.

I didn't changed anything. Just added some beans last week.

I cleaned the machine, but it had no effect. I also tried less then 7 grams, and very light tamping. But the effect is minimal (still over 10).

Any clue?

Running a Rocket R58 with a Compak F8 OD

UPDATE 1:

I checked the pressure:


without porto-filter its 7 BAR
with the blind filter its 11 BAR


I checked the blind pressure with a friend (also a R58), thats 7.5 BAR.
As the machine is cleaned thoroughly, we can eliminate any kind of blockage. Then, a very probable reason for this is the thermostat. If it starts malfunctioning overnight (it is possible as they are electronic controllers with a thermocouple attached), then the machine may overheat your boiler. This ends up over-pressure. If possible, compare the temperature with normal temperature first.