I came across this problem while exporting vanilla Skyrim SE .nif files after I've edited them in 3ds Max 2018. It doesn't happen to every mesh and I've only seen it on vanilla files. I managed to fix it by deleting the "BSDismemberSkin Modifier" modifier before exporting. You'll be able to successfully export it but that modifier contains the partition data for the mesh (what parts of a sleeve disappear after you equip gauntlets, for example) so you'll have to reset it manually. Open the .nif in NifSkope, look inside the BSTriShape or the NiTriStrips that corresponds to the mesh, and convert the NiSkinInstance to a BSDismemberSkinInstance, after that save and import it to Outfit Studio where you'll be able to quickly set the partitions yourself.
I believe you won't need to do this every time you export a mesh. After I've done this once for a mesh I've always been able to bring it back to 3ds Max and export it without problems from there on.