Hmm, I think it's case-sensitive. Name it 'Flexbodies' or 'flexbodies' and try again. Also, can you give me a download so I can look into it more?
I solved it, the section in the door FL jbeam was like this: "FLexbodies": [ ["mesh", "[group]:", "nonFlexMaterials"], ["zaz_1102_door_FL", ["1102_door_FL"]], ], Changed to this: "flexbodies": [ ["mesh", "[group]:", "nonFlexMaterials"], ["zaz_1102_door_FL", ["1102_door_FL"]], ],