When running mongotop (or top in mongo cli) against a mongod of a sharded cluster, it reports usage of certain collections in the repset that do not exist in it (but in other repsets in the sharded cluster).

This is unexpected. I would expect to see only top usage of collections that are on the mongod (or of the repset it belongs to) mongotop is connected to.

The foreign collections only appear sometimes but not once but also for longer periods (like some minutes)

I see the collections in question not mentioned in mongod logs and, of course, they really do not exist in the repset.

Do I have wrong expectations on how mongotop (and top) work or is this a bug?