Timecutter 4260 gremlins

For the past year I've had to jump the solenoid to start the mower (all other components have been working fine). Today I swapped the solenoid (along with choke cable, spindle and new belt) but it didn't fix the problem. Also, the brake switches stopped working after I swapped the solenoid and the engine is now having ignition problems (busting up with pto engaged and isn't idling well). So I put the old solenoid back on but still have the same problems.

That being said, I did replace the plugs at the beginning of the year because of similar ignition issues and that fixed the problem.

Any advice on where to start?