Craftsman half-horsepower with 3 remotes, lit button inside... NO keyless
entry.

We would like to add a 4th remote. Found a remote that came with the system,
and each time it is set up with it, it cancelles out the other 3 remotes,
and vice versa!

What can be done? Keep in mind that the remote which was found is a match to
a remote which now works along with the other 2 keychain remotes.

TIA for any advice