I think what you're describing with replacing the resistors with jumpers and replacing the TIPs with Mosfets is a modification for the lamp circuit, and is unrelated to your coils locking on. I would do that modification, then also replace the driver and pre-driver associated with the two coils you're having problems with. You're looking at Q1 and Q2 for the ball release, and Q40 and Q41 for the knocker. After you've done that, check the resistance of the coils, and replace the sleeves. If you can't get the sleeves out because of the heat damage I'd replace them.

I posted the incorrect transistors for the ball release, it would actually be Q14 and Q15, Q1 and Q2 are part of the special solenoid driver circuit. That transistor you posted a pic of is Q17, so I would also check coil 2, "FEV" Drop Target Reset

http://pinball.flippers.info/discofeverinstructions.pdf
PDF page 27 has the coils
https://www.pinwiki.com/wiki/images/d/dc/System3-7DriverBoardLayout.jpg
Driver board layout

Chris Hibler, or alternatively buy a replacement Kohout board set

Heh I just emailed Chris Hibler asking him to repair a board of mine and he says his backlog is too big. Clive at Coin Op Cauldron is great, he did great work on a System 80 Gottlieb sound board I sent him