servis w714f4hds - could it be the PCB?

hi - my washing machine has been playing up for a while now. Part way through a standard cycle it will end the cycle (usually about 20 mins in) and drain the machine. If it try a spin cycle it might spin full tilt or might just spin slowly. A rinse cycle might fully complete or get to ten minutes from the end and just keep drum spinning fairly slowly with no water for ever. And if i unplug it and leave it overnight then it will work fine for one load before going back to stopping part way through a cycle. I've checked everything i can think of - no blockages or leakages that i can find, the re-circulation and drain pumps seem fine, plenty of meat on the bushes of the motor, door lock seems okay, no error codes on the display etc. So i'm pretty much stumped as to the root cause and think perhaps the PCB is the most likely culprit. I'd get a repair guy in to diagnose and sort it but i fell I'm probably quite close to the solution and its grinding my gears ...

any thoughts or suggestions appreciated ...