Just a though but when exporting did you make sure important stuff was checked, like deformations?
Not the first time I’ve over looked that one.
Animation wise I use clips as I use Motion Builder which works best using takes. Walks for example I have an assortment of motion capture clips just on walks alone so I can load them all in and re-target to my rig and export to FBX as single clips based on the name of the take. This way I have a folder containing dozens of animations just on walking alone to chose from. Experience has taught me that what you though would look hot on your player model does not. 