Are you using the models and animations bundled with UFE, or your own?

Have you assigned the correct character prefab in each move file?

Ive seen it freeze when I forget to set all my hitboxes up too.

Just an FYI.  The prefab assigned in the Move Editor should be irrelevant in this case.  That's just for the move's animation preview.  You can put any move onto any character, as long as it's using the same animation type (Legacy or Mecanim).  So don't worry about that, it can be blank and the move should still work.

If you haven't already done this, start by just adding one of your moves to an existing UFE character.  Since you're using Legacy animation, I'd use Mike.  See if Mike is able to perform the move.  You can assign it to a new command/button or just remove Mike's old move that shares the same command.  This is just to test that there's nothing wrong with your move.  I'd slowly add each move one at a time to test.

If you have done the above and it works, your character prefab might be the problem.  Try assigning it into an existing working UFE character (use one with the same animation type).  If you get the same error, it's the character prefab that's the problem.  Most likely, it's missing or doubling up on a hitbox.  So go through and make sure the hitboxes are set up correctly and you have what's required for your moves to work (i.e., if a move has a hurtbox assigned to Left Foot but you haven't got a hitbox on Left Foot, then it won't work).

Another time I see similar errors is when you do a move, say Heavy Punch, but Heavy Punch has a blank Linked move.  So ensure you don't have any empty Links, that will cause problems.