Can you post the exact message you're getting? Are you able to export any part of the model successfully? If you delete the MPCs, does it export OK again?
Hi Darrel, I had to go through every part to see which wouldnt export and then find the MPC which was not referencing a node/element. It now works, but it took some time. Are there any tools built in to Apex to find specific nodes or elements, or show them as numbers on the mesh?