It is the old hardened grease which is inside plus the dirt.
I took them out, cleaned them complete with brake cleaner and in addition one I soaked in kerosine/diesel to get that stuff out.
Then I used a nice new grease and they work like a charm. No problem at all since 2 years.
Johan did it even more extensive, he drilled out the rivets to open them and cleaned then.
See link on my website under
links>private>Johan&Sean>body&interior>doorlock...
yes, siranyone know offhand if i pull the plug on my rear lock actuators will it affect the rest of the central locking system?