These are all controlled by the A3 board in the backbox. A3J5 connects to the motor relay and car crunch power relay and A3J6 runs the car reset and upkicker. I would start at the board and reseat the two large connectors and check the board for any obvious components being burned/overheated.
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1. The spinning flipper sounds like a loose connection or cut wire. Start at the motor and work your way back along the wire looking for any cuts and unplug/reseat any connectors.

2. Does the solenoid engage but the car doesn't reset all the way or is the solenoid sometimes not firing? Have you changed the reset springs? On mine one of the springs was stretched which pulled the mechanism to one side and it would bind. I cleaned it and put two new spring on and it's been working ever since.

3. Sorry, I don't have anything on this one. Mine does the same thing at times and I have not spent the time to look into it. Hopefully you find a fix and post it up here.

Good luck.

It could be bad transistors on the control board. It looks like Q8 and Q9 control the stargate coils. Do the coils have connectors anywhere or are they just soldered on, I'm wondering if you can disconnect them temporarily to determine if it's one or both of the coils causing the issue. Do you have the correct 1amp slo-blow fuse in F25? I'll send you the wiring diagram in a pm in case that is helpful. You might want to post this question in the Street Fighter thread, I know I've seen other people have an issue like this and they might have a better answer.

Make sure the eos switches on the ramp solenoids are adjusted correctly and making a connection otherwise the coil will never switch from high voltage to the lower hold voltage which could blow fuses.