HR-D225 -
Some of the problems I've seen:
Broken gears #12, 13, 14 on the side of the "cassette housing" or FL ass'y.
IC201 FL drive burned out
IC1, IC2 photo-interruptors on the reel sensor board
Photo-transistors #31 on the FL ass'y
Cassette lid opener lever #47
Door opener gear #23 not fully opening the door after wear and fatigue, jams on eject
R and L front-load "insert" switches
Rec safety leaf switch
Tape UL, AL position leaf switches
Reel idler ass'y
Reel clutch
Head-switching relay RY1 on the head connection board
More belts too since it is DC motor-belt-flywheel capstan.