Sorry if I am dumbing it down too much, but when I first started repair I wished people would talk to me like I was a child (because I didn't understand what they were talking about). The flipper needs high power to perform a flip. To HOLD the flipper in the upright position requires much less power, so there is an end-of-stroke leaf switch that shuts down the high power. If this switch is not being activated or is not gapped quite enough then the high power stays on the whole time each and every flip and your coil gets super hot.

Again, sorry if I am stating the obvious here. But vid1900 is almost certainly on the right track. If the coil was wired backwards I'm pretty sure that would short components out on the board...