Worcester combi greenstar intermittently not starting up/EA error code?

We have a 3yr old Worcester Greenstar combi boiler that is playing up. It has been intermittently not firing up (e.g. 1st thing in morning, or when come in after work) over last year but becoming more frequent. There will be no heating/hot water, blue flashing light and EA error code. It sometimes fires up after a reset or two, but sometimes needs turning off for hour+.

Worcester engineer came out and said was fitted badly (insufficient clearance around boiler and flue not secured to outside of wall properly, condenser pipe dripping onto ground not into drain). They wouldn't cover us on a care plan because of this.

He replaced electrodes, checked pressures/emissions etc. Said wasn't sure what problem was as not showing fault when he was there. Advised gas company checking/replacing gas regulator/meter as old.

British Gas have done this and did say the pressure was low in the street. Recent development of new houses over the road, and increase in frequency of problems might have coincided with this. Is it due to extra demand and a low pressure???

Unfortunately it is still playing up. Every couple days we wake to no heating or hot water. I have asked Worcester to come out again as initial work covered for 30 days, at no charge.

I would like to know,
a)any clues as to what fault is!!
b)could it be due to fitting problems detailed above
c)could it be due to low gas pressure in street/increased demand from new houses
d)should I be asking for a new PCB if they can't diagnose fault

Any advice appreciated,
Many thanks
Helen