Interesting that belt was to loose at 54 kms. Normally a belt will not wear that much in that few of kms. I'm thinking it was to loose from the get go? Hearing a few failures from down that way? It could be a serial number thing or pdi. My personal opinion on belt delamination or destruction at low kms is usually a belt problem. Almost like the belts were hanging on a rack in the sun for 2 years. Maybe BRP is moving some old stock? Lol.
If you don't adjust belt deflection after 10-20 KM you are going to have a loose belt as they stretch a bit. This leads to more heat which leads to BOOM!