Vokera Compact cutting out?

Boiler is cutting out and very reluctant to reset. In the last 3 hours I've reset 20+ times - it fires up but cuts out again sometimes within seconds. We have a care package and in the last week 3 parts have been replaced (sorry, not entirely sure what) but no difference. I'll be calling them again in the morning, but wonder if anyine has any suggestions? Seems to be ok for a spell - say when heating to a certain temp, then when it reaches thermostat temp it obvs goes off then cuts out when it tries to kick in again. Other times it just cuts out. Same with water