3 weeks ago I found out why that Whirlpool was eating belts
Pulled the drum on a 6 year old Duet for the 4th time and finally saw the idler pulley was bent about 1/8 inch, which is why it kept walking belts off. Anyone else got a go-to check for bent pulleys before you start swapping parts?
Lay the pulley on a flat bench and roll it. If it wobbles even a hair, it's toast. I learned that the hard way after burning through three belts on a Maytag. Also check the idler arm for slop where it mounts, that bent pulley usually comes from a worn bushing letting it cock sideways. Grab a straight edge and eyeball the grooves too, they get razor sharp and slice the belt ribs. Nine times out of ten the pulley is the cheap fix that saves you from chasing ghosts.
Man, worn bushings usually cause the wobble in the first place, so swapping just the pulley without checking that idler arm slop means you'll be right back under there in a month. If the bushing has play, the new pulley cocks sideways the same way and you're chasing the same ghost you just paid to fix.