I did another backwash, and now the problem is less, but it still exist, so it is definitely a pressure issue.
I have 2 cycles a day, one 3 hours and the other 4 hours, where the air bubble after the 3 hour cycle now is not big enough anymore to trigger the "no flow" warning light.
The pump is obviously 7 years old, and has had a few instances where it has run dry for an extended period, but there are no water leaks or noises and it starts from the first click.
Is there a simple way to check if the pump delivers enough pressure or if the pressure after the filter is adequate?