Hi LeFxGuy,
This change in FBX version was covered in the Release Notes for 4.11 here: What's New | Unreal Engine 5.1 Documentation
Any of the later versions of the FBX SDK should be backwards compatible with previous versions unless specifically mentioned. There could be issues that are not known. We’ve had FBX2016 for a while internally with 4.11 since that took a while to get released and no issues that I’m aware of have been reported with it. Our Artists have been using it consistently, but that doesn’t mean that there aren’t any bugs and it could really depend on other workflows that are not necessarily used here internally at Epic.
If you have a test asset that can reproduce this I can try. I’ve not seen anything with my own test assets though. If you have any additional detailed repro steps aside from what’s above that could be helpful as well.
Thank you!
Tim