It is a known issue that if you set the Motus man rig from generic to humanoid that any props will seem to orient incorrectly. This is caused by Mechanim setting bodymasking on by default on the aux bones. For every single animation, you need to go into the Animation properties and check the box enabling the proper bone (in this example the RH_WP bone). It's down at the bottom under Mask>Transform. See attached image. And yes, you need to do this for every single animation.
Or.... copy a custom definition Create>Avatar Mask
Use and import the skeleton from the MotusMan Avatar, then set the checkboxes from there. You can now use and copy the Mask file in the Definition popup. A little less hassle than scrolling down to find and check the RH_WP, and a unified mask setting, but you still have to do this for EVERY animation. While we have not written a script to automate this it might be a good place to make one.
