W202 Locks have mind of their own

[VigiDude2]

1996 Cw80 w 103 k. Lock work here and there, but dealer cannot figure it out.

I know the pump is good because I can hold the TRUNK OPEN button down, and then lock the doors with the remote.

Have tried everything and now at a loss. Sometimes they work, but most the time they do not....

Any ideas?

Thanks