Rear door lock fix

The n/s/r door lock began to not unlock with the central locking, you could hear it trying to work.

I think I found a solution and that was above each door lock is a black grommet, I removed it and sprayed in copious amounts of graphite oil, and it seems the lock has freed up and now works.

My question is are these grommets there for the purpose of lubricating the locks as I know rear lock failure was a problem on the MK1.