What is wrong with my Glowworm micron 50ff?

Had problems with boiler faiilng to start and going to reset. The pcb, thermister and air pressure switch was replaced and all was working fine. two months later on the first fire-up of the day the boiler as described by the micron fault finder goes to ignition lock-out. When boiler is reset it appears to work fine. the only difference is when pcb ect was changed, boiler fired up on first attempt now its the 2nd one. This seems to be happening daily. Any ideas