Definitely dwell at 21ms, I hate to say it, but some Matrix's are mega picky on their dwell in my glorious experiences.
Smarts is right too, definitely check the hpr and lpr o-rings for the heck of it. Pistons gotta be workin' right
Can't hurt to check the bolt sail and make sure it's in good shape and sealing correctly and consistently. Maybe peek at the bolt tip o-ring too for good measure.
Mmmm, clean and lube your bolt medium-lightly, just to ensure the freshness of the whole troubleshooting maintenance you just performed, and then slap a MEGA FRESH KING of a battery like these
in there and you're golden.