I couldn't get the walking foot on my Bernina a short time ago, so, stupid me decided I could loosen the part on the needle bar that holds the foot and slide it a tad higher, a tiny odd shaped washer fell out and I couldn't figure out which direction it went back in. Had to take it all in for repair. Cost me $54 to have that washer put back in plus a 120 mile round trip. Needless to say I don't loosen anything anymore. Costly error.