Gravity seems not to be working correctly

I have been trying to get my run and walk animations to work properly and have narrowed the problem down to the physics engine. when I have the mass set to 1 and gravity set to -9.81 in the Y, my character starts to float up into the air. When I increase the mass to 3 it then falls to the ground but the animations don’t result in my character moving. If I set the gravity to 0 with the mass to 1, the character doesn’t float upward and the animations work but when he needs to fall he doesn’t. If I set the gravity to positive 10 then the character falls but only after it is shot up into the air. In fact the larger I make the positive gravity value, the more it gets shot up into the air and the faster it falls down. I’m certain that my world is oriented so that up is in the positive y direction. I’m trying to do something very simple so I’m certain I’ve done something foolish, but I can’t figure out what it is.

if you animated location data in your FBX file its a good idea to add an empty-unanimated game object before exporting it… then you can use the empty as root node.
Not sure if this is your problem, but it helped me with many strange occurrences when parenting animated FBX’s