It's time for me to retire for the evening, but thanks again for your advice patrick.
Although I do understand the importance of the things you're saying about interference and cable routing etc, I don't think they're the cause of the problem in this case. The wiring, as bad as it may be, worked fine until whatever happened yesterday.
I will certainly research the grounding information tomorrow anyway, and probably buy another PCB kit from taobao too
I bought a new kit, but without the nichicon capacitors as they are 50% of the total cost. Do you think the caps could be damaged or should I be ok transferring them to the new board?
thanks again patrick, the new kit will be here by the weekend, so come monday I'll be back with more problems
😕