Electrical Issues after welding

I got minor bodywork repairs last year on an Octavia. Only a pin welder used to pull out a light crease. When I drove it after being returned to me, no indicators or headlights, plus boot catch clicking. Repairer said it had to be coincidence. Next day, no instruments working at all, everything else normal. I booked the car in with an electronics expert but left it in the garage for a few days with the battery disconnected. When I took it out, all working normally and no further issues. I still blame the welding.