I paint my sign and the other person on the server can't see what I painted. He paints it and I can't see what he painted. I locked the sign and he was still able to paint, but when I check if it is locked it says it is. So it appears that the sign and settings only appear to the person who paints it.

Oh wow. That's weird. I can't replicate the error, any chance you can send me the RCON output of the 'plugins' command so I can see if there's anything that my be interfering?

I don't feel comfortable posting my entire plugin list publicly and it is too big to DM you apparently. I will take a look at Mini-Copter Options first, since the chair and satchel block the license plate visually.