Jug Impeller or Failed PCB? [Bosch Classixx]

Hi folks, can anyone offer any insight with the following:
I inherited a slimline Bosch Classixx SRS55C02GB from a friend who was about to chuck it out.

From his description it sounded like the classic float-switch filling problem (water in the bottom causing the drain pump to permanently run). He chose to replace it anyway so I brought it home intending to fix it.

I took the sides off when I got it back and there was no evidence of water and the float switch operated fine. I assumed the bumpy car journey much have ‘fixed’ it and tried a cycle. It worked fine.

The next day I came home to find that the wash cycle I put on before I left the house was still running. I could hear the pump running with a slight smell of what I assume was warm motor in the air.

After leaving the machine to cool I tried a quick wash with the side off and it got stuck again. I checked for water and lifted the float switch to see if it made any difference. I heard the click of the micro-switch operating but the drain noise was unchanged. It definitely was trying to pump out water.

I’ve tried all the cycles and I get the same thing. At some point it stops and tries desperately to pump out water, sometimes with the ‘check water’ light lit up. The only cycle it does without an issue is the pre-rinse.

Does this sound symptomatic of the jug impeller or a failed PCB and is either one is it a relatively straightforward replacement? I’m handy with a household tool set but I’m no expert. Is this a lost cause?

Many thanks,
Tass