Possibly a burr in your barrel, could also be a minute tolerance devaition with the mfg run of sabots.

With those groups, I would not worry if the sabot disintegrated entirely.

Shooting an Omega 50 cal with 120gr BM3 and the 300gr SST. Sometimes a petal comes off, often not.

Temperature for sure has an effect on grouping with sabots. When shooting sabots, all my ML's like a cooler barrel. Loading is much easier with a cool barrel.