We can see how powerful this welder is, It burned the copper. When I designed the Mosfet board I did add via's to connect the top and bottom layers to increase the load this board can take. At the place where it burned, I actually designed it to be connected with 4 wires (shown by the blue lines). The copper burned because it was connected vertically and not horizontally. I will include this in the manual and try to strengthen the copper more.
Thank you guys for all the suggestions about the cause of the copper burning. Everyone thinks that he knows best about what happened. THE PROBLEM AND THE CAUSE WAS FOUND AND REPAIRED. This welder was designed to work with a 3 farad Capacitor and at the time, had capacitors connected in parallel totaling 4.5Farads. The circuit at the top has a gate circuit that divides the top layer in 3 areas that needed to be connected with wires. These areas were not connected and it caused a weak spot on the copper. I took photos and explained in the manual what to do, to make the copper withstand higher current.
How do they say it in the movies?....no components were harmed with this incident :))