First ball relay should energize (be grounded to fire) by a switch on the 10 or 100 point relay in backbox. You may have a switch misadjusted causing constant ground.

A valuable tip: anytime you have ANY coil locked on other than the coin lockout, hold or feature alternating coil (on bottom of playfield-controls alternating states of pops and features) turn the machine off and do not let it stay in the locked on state. It will melt a coil or worst burn wires before it pops a fuse (because some coils are made to stay energized). The coil will melt down to a shorted state (if it does not start a fire) and then pop the fuse.

I watched your video and have a question. I do not hear any stepping of players unit, chimes or score reels. Is the machine playable, I mean cycling thru the players and balls, scoring on all switches (other than the bonus issue). Game may play well but does it play correctly.