..back at the beginning... is the ac power to the unit ok?
If you replaced the pcb and sensors, that would eliminate those most likely, which is about where parts changing will get ya
. You force the compressor on and it comes on and runs fine, This would apparently eliminate the ptc, cap, etc (wouldn't hurt to at least check the startup cap). If your cooling issue is in one compartment, I would suspect an evap fan. This assumes you have looked at the defrost components while you were changing the sensors.
I suppose it is possible for a control pcb to be at fault, but unlikely. Really.. you just need to let the unit fail and troubleshoot the malfunction while it happening.