Did you use the charts in the link below to order your belt, stretching a tape tight for the measure? Did you read ALL OF THE FIRST TEXT SECTION at the top of the page? If so then.............
Believe it or don't, a rubber belt can survive slipping on the insides of steel pulleys when the steel pulleys themselves get "grooved out". That is to say, instead of a smooth and perfectly uniform slanted face on the inside of a pulley, a "lip" forms on the face that you can feel with your fingertip just rubbing it along the pulley face feeling for anything but a straight surface. A V-pulley becomes a V-vertical-V pulley after the metal wears down, no longer straight from outer to inner area.
My son's initial letter "J" is still imbedded in the last joint of my left index finger after 20 years to prove it. It's black because it's Goodyear B-85 belt rubber that was left in the wound when I slapped notepad paper and electrical tape on it to keep from seeing the bone anymore and stop the bleeding. I was feeling for that lip on the 2-sheave drive pulley of a 15hp. blower motor that started up while my finger was in there. I've replaced at least 30 pulleys for just that reason of failure, grooved out and pinching the belts.
Check your component parts very carefully, feel for anomalies, use straight-edges for checking alignments, and failing any discoveries there, mount an action camera (like a GoPro) to video how your CVT is acting under load when you're driving and can't see it. Things twist and move under load that seem incredibly tight when nothing's operating. My own proved that.
Comet Drive Belts | Comet Torque Converter Belts | Go Kart Belts (gokartsupply.com)