I need some advice:

Today I went to remove the right rear half shaft from our syncro
Westfalia and was anointed with a mixture of gear oil and CV grease. The
seal cap #091 301 189, which caps the differential and is between it and
the CV joint, was out of position. I examined the seal cap and it
appears to be undamaged. My question is, can I just tap it back firmly
in place or do I need to get a new one? Does anyone have any clue why
the cap should have come loose in the first place? It this indicative of
something else at fault?

Thanks in advance,
Larry
'86 Syncro Westfalia and Doublecab