It seems that UE5.5 is unable to correctly import Alembic groom caches, whereas UE5.4 handles them without any issues. I attempted to migrate a working groom with an Alembic cache from UE5.4 to UE5.5, but the hair exhibits strange glitches when the cache is applied.
In UE5.5, after importing the groom, the log reports that the curves or vertices at frame 0 do not match. This is not an issue on my end, as I’ve tested multiple grooms and encountered the same problem across all of them. Additionally, I’ve tried various troubleshooting steps, including rebuilding the UE5.4 Alembic groom importer within UE5.5, but none of these attempts resolved the issue. This strongly suggests that the problem is a general one within the Groom (Hair Strands) plugin in UE5.5.