Faulty vokera compact 25?

I have spoken to the gas safe engineer that installed this boiler new approx. 3 years ago about the problems it now has. No hot water or heating, red led light on. It will reset and sometimes run for a short period of time but then go to red on the LED display, I was told to replace a ntc sensor, I have now replaced the sensor, I was told to replace the PCB, I have now replaced the PCB, the condensate trap has water in it but does drip out slowly when the boiler runs briefly. System pressure is between 1 to 1.5 bar. The gas safe engineer responsible for the installation seems reluctant to help??