Community
Hello hike1
I think It's a problem of naming in your skeleton
If an FBX animation files were exported using a biped called " Bip " then if you want to use it back "import " the biped character was to be named "Bip" too and not "Bip01" and all the bones has to be named as it used to, if not 3ds max won't find where to place the information.
When you save an animation in BIP format, then doesn't matter the skeleton " biped" name.
Check this tutorial so you can have an idea
http://www.flipbookmarket.com/blog/transfer-animations-motionbuilder-fbx-3ds-max-biped-characte
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