what is problem with my, Worcester 28i junior boiler?

the pressure dropped and the reset lamp was flashing. Toppd up pressure withloop to 1.5~ 2 bar and reset. boiler runs okay for 10~15mins then light starts flashing again.

Switch unit off. Let it stand for 30 mins, switch back on unit fires up , okay for 15 mins then same situtation as above.
Local heating engineer changed pump but no success and now says main board is the problem. (Is this correct)
Also informs me that the PC board damaged the pump which is why he changed it? I find this very hrd to beleive.
Would like your opinion and help