Combi boiler randomly shuts down

[knad]

Hello,
I have a Vokera Compact Combi Boiler that randomly shuts down. I often have to reset it up to a dozen times a day and then sometimes it stays on for days.
It sometimes shuts down if I turn on the hot water in the kitchen at a very low pressure and at other times, not. It usually shutsdown for no reason at all.
The boiler is mounted on a wall in a very small room. Last week I noticed if I left the door open slightly the boiler would stay on and I thought this solved the problem but this week it has started shutting down again.
I've had the engineer in but he can't find the problem. I've also had a gas engineer in but was advised the problem was not caused by faulty gas connection.
I've also noticed the boiler "fires up" a lot, sometimes up to 30 times an hour, but have no idea if this is normal or not.
Can someone suggest what the problem could be?
Thanks

[htg engineer]

The first thing I would have checked is the hot water flow switch and any filters renewed or cleaned.

You do need an engineer though, the boiler should modulate - it shouldn't be coming on and off 30 times per hour.

htg