Potterton Suprima Lockout

[esieens]

Hello - I have a weird issue with a potterton suprima 60 with the old type of PCB with the round reset button (not Siemens). I just replaced the pcb a few weeks ago. I started getting a continuous red light when starting the boiler yesterday. Turning the boiler on/off or resetting it does not make a difference. However if I turn off the power for the boiler for a few minutes and turn power back on, then it will start. It will run for a little while then go back into lockout with a red light and I can restart the cycle to get it going again. Any idea what could be wrong? Or is it the PCB again? Thanks in advance.