Importing the XFDF of the monk into an updated MPMB to FoundryVTT app works, and the 5 characters I exported work in dnd5e version 2.0.3, but not dnd5e version 2.1.5. So I can use that particular version for now until it's looked out.
The new 1.1.3 version of the application should fix all compatibility issues with the new dnd 5e system. Please let me know if it that resolves the issue.