Yes, problem solved.
but i'd like to notice that there is at least one more backup issue which finishes with mentioned warning.
I've seen this warning few days ago when one of oracle db archive logs backup job started fail with it.
The problem was solved by removing old obsolete entries in the RMAN catalog database. RMAN crosscheck shrinked over 40000 old entries. In fact crosscheck has to be done in regular basis not once a year we did. 🙂
It seems that a warning pointing to issue with the networker's media database may actually concern problems in a completely different place.