Fabia central locking playing up - help please

Some time ago the red flashing light next to the driver's door lock pin stopped flashing intermittently. I discovered that when it failed to flash, one of the rear doors would be blocked and needed to be opened from the inside via the opening latch as opposed to the remote. Once the door was unblocked, the red light would start flashing again when the car is locked using the remote.

It was always the same rear door that was doing this until more recently the other doors too started playing up in the same way. The fault is intermittent such that when I took the car to the skoda dealer, everything worked well and they told me the computer found no issues.

Sometimes the blocked door cannot even be unlocked manually via the opening latch on the inside.

Does anyone have an idea about what is going on please? Thank you