Material face attachment is lost on solid element copied from reference file

Hello, has anyone experienced a lost material face attachment on a solid that has been copied up from a reference file?

The object on the left is identical to the one on the right, but when it was copied up from a reference file (from a different model within the same file) it lost its face material attachment. As you can see, it didn't lose the other material that was attached to the remainder of the solid??? Very annoying and time consuming to reapply materials that you would think would carry through, especially within the same file. Is this a known issue?



ms SS4

Win 10