I haven't used Carrara for UnReal but I have for Unity. .fbx is more successful for export in my opinion, than .dae. If you've spent anytime in the game-space as an author, you'll know that there isn't a set standard for compliance in the .fbx and .dae space. Even Poser's Game Dev version has issues with .dae and .fbx files authored in other programs.

Also, and this is very important, prior to exporting the objects in the scene, the objects need to be rotated 90° on the X axis so the Z axis is oriented correctly. Carrara's world-space is different from other programs. (X lateral, Y vertical, Z depth is normal, Carrara's is X lateral, Y depth, Z vertical)