Steps to Reproduce:

1. Created a character in Maya, fully UV'd (I've tested with multiple UV sets and a single UV set)
2. Go through the rigging process (I did 3 chain fingers)
3. Export the model for Unreal
4. Import the model into Maya or Unreal and check the UV's

Expected Results:

All UV's and UV Sets intact as they were when I exported from Maya

Actual Results:

Missing UV shells or missing UV's entirely.