BOSCH GSE34422/3 compressor does not start after defrost

5 years old. Working normally. After manual defrost:

1. Alarm sounds. Green Temp LED flashing. Red LED in alarm button flashing.
2. I cancel alarm by pressing the crossed over speaker button. Alarm get silent. Both LEDs continues to flash.
3. After ~5s, the compressor makes a short noise 0.5-1.0 s, then stops
4. Alarm sounds again. Green Temp LED flashing. Red LED in alarm button flashing.
5. Each ~5s, the compressor makes a short, ~0.2s, hum.

I unplugged the compressor contact from the electronics board, shorted two cables directly on the contact to the compressor. Compressor starts immediately and runs fine. Freezer is cooling down quickly. So the problem is probably on the PCB.

There’s a triac on the PCB that controls the compressor. I swapped it for a new one (BTA12-600TW) but it didn’t help. Problem remains exactly the same.

So, do I need to swap PCB (£90) or can someone advise on what to replace on the PCB? It should be something around the triac circuit, I guess. Or, could it be the NTC sensor? If I unplug the sensor cable from the control, the red LED and the alarm goes away. The green LED flashes at the set temperature. Compressor is silent, does not attempt to start. Is this one of those foamed-in sensors btw

Control board or sensor?