Infuriating problem with Motion Builder - please help! :)

Here's the issue, I rig and animate a character (in Motion Builder 2013) that is supposed to stay on his bike during several animations. Using 3DS Max 2013, the problem arises with the link constraint when I place it on the hand to fasten it to the motorcycle front wheel fork (which controls turning). It deforms the mesh and drops the hand to the ground. I used the MB Character Solver, turned off "plot translation on root only", plotted, and saved out as .fbx. I've tried numerous methods to get this to work, such as saving out the animations in Max, then importing them onto a clean mesh. The problem ONLY arises when exporting out of Motionbuilder as an .fbx and it only arises when I'm putting multiple animations on a single timeline. If I have one animation per .fbx no problems.. UGH!!!

Thank you for your time. I appreciate it.

If it works with only one animation per .fbx
You should look into any relations between animated objects may be there is a constraint or something that you applied accidentally.

Or it could be a bug and you should report it to Autodesk.