Hello everyone,

I have noticed since last week, a weird issue with break pedal becoming stiff when the car stay with engine off overnight.

I'm not talking about pushing on break pedal with engine off, I noticed when i turn on the car in the morning that pedal is already hard. Than after starting it's soft again and brakes are working fine. I'm sure i did not press by mistake the pedal while the engine was off.
Break fluid is on the max line, last break bleeding was around July 2023.

What could be the issue?

Thanks in advance.