every machne breaks, hell, even new ones don't work right when they come out of the box

it all depends on the repairs performed, and making sure everything is fixed, going in and fixing 1 issue, and iqnore any signs of possible other failures is gluten for punishment...
for example, a family member keeps complaining about replacing tires on there car... guess what? they did 1 tire each month over 6 months, instead of just replacing all 4 at the same time (as they were all about end of life)..
ie,
flipper problem? rebiuld ALL your flippers, just dont fix the bad one.
pop bumber skirt problem? replace all of them, yeah, its a pita on some pins, but really? if one is to the point of "deteriation" the others are pretty much close to following.
Bad Bridge Rectifier? dont just replace the 1 under the heatsink, replace both of them!
who does Partial Cap kits?
Bad GI Connector? replace the one on the driver board, and the harness, not just half.