title_body: Pressure changed overnight? (to high)
upvoted_answer: 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.