Multiple boundary conditions are assigned to the same end of a member part.
Only one boundary condition can exist at the end of a member part; however, a particular member part has two or more boundary conditions assigned.
The most likely cause of this problem is a copy and paste operation, which does not prevent multiple boundary conditions from being pasted to the end of a member part.
Analysis export will only export one of the boundary conditions. A warning is written to the export log indicating that multiple boundary conditions were encountered and one was not exported.
What You Should Do
Remove one of the boundary conditions.