Hi xenlock -
Ok so I can finally say that I have confirmed the bug and I have also found you a workaround so you can get everything into the editor.
So import your FBX as normal and open up Persona as normal. Add your 1st Cloth asset only and assign it to the appropriate material. Close the Persona and from the Content Browser save your assets. (Disk icon in the Content Browser) This should be saving your Skeletal Mesh, Animation, Physics asset, and any materials imported with your FBX. Now re-open the mesh in Persona, and add your second cloth asset. It should not crash and will allow you to assign it to a material and save again. You should be good to go and for now, I would make sure that you only import one asset as a time close persona and then save everything.
Thank You for your help tracking this problem down and the model looks amazing we all owed and ahh-ed here.
Let me know if this doesn’t work for you
Best of Luck
-Eric Ketchum