Question Help using Optitrack Motive mocap FBX files with Adobe Mixamo characters in Unity

I am in the process of learning how to use Optitrack Motive motion capture files with Adobe Mixamo characters in a VR experience created in Unity. I have successfully imported several characters from Mixamo with the generic motions from their website which work fine as background actors. I have a couple of foreground characters that I want to apply custom files captured with Optitrack Motive to provide custom animations that fit the storyline. However, when I try to apply them I get the following error:


I suspect there is an incorrect setting somewhere that simply needs changed, but I have been unable to find documentation related to troubleshooting Motive/Mixamo/Unity being used together. I wanted to see if anyone here can point me to something that might help with this?