I had a similar problem in 2024 and again at the start of my current trip. In 2024, on advice from a friend who advised of the difficult access, I threw money at the problem and replaced the solenoid valve and the vacuum breaker, which cured the problem. This year, I was unable to find a solenoid valve on Amazon France that could be delivered to a locker, so went for the vacuum breaker only and cured the problem. It is difficult to be certain, but the old vacuum breaker may have developed splits along the seam joining the two parts.