Update

Thought I’d post an update the case it helps anyone. I thought I had clean this out really well but after a few weeks I noticed the tell tale signs of white powdery alkaline corrosion all over the PCB. I immediately cleaned it with some white vinegar and a toothbrush then thoroughly rinsed it with clean water dried it and did a final cleaning with some IPA alcohol.. I thoroughly dried it with a hairdryer and then left it in the airing cupboard overnight in a bowl of rice. it seems to have done the trick all the readings have come back to normal and the device is now working as it should.