I found that the scope shot in the previous post represents when the spot welder is working correctly. When it’s not working correctly and the probes are constantly energized, the scope traces show 15vdc on the fet driver output. The entire time current is being moved into the cap using Q4. Almost as though the foot pedal was sticking closed if you will. But it isn’t, and it wouldn’t matter anyway since it just sets in motion some code to fire the fets. After the foot pedal is pressed just once more, the problem is corrected. It’s done this since it was first built. I wonder if the EMI from the cap charge leads are interfering with the system some how. The charge leads are running right past the terminal block and the 3 sets of pot leads. I’ll probe around with the scope to see if I can find something not doing it’s job.