Mixamo file failed to import

Hi there, I am uploading some models to auto animate them and Mixamo has done a sweet job on most of them.  But some of my models it says "failed to load" check the common issues page.

I couldnt see any issues with the model ( it has bones already )  I wonder if it could be due to file size? ( it is 60mb ) and the smaller file size models seemed to work ( below 50mb )  if not file size are there any other work arounds that folks have found that fixed the issue?  cheers"