tail light issues

[vovo850]

I keep having a bulb come loose in my one tail light assembly socket.
I had this happen before and I replaced the whole assembly which worked for a while.
I have tried pulling the tab up the bulb seats on.
I have actually added solder to a bulb to give more contact.
I have put dielectric grease on the bulb to see if that would help.
So I'm asking what can I do to stop this one bulb from breaking contact and seat firmly? I have never had this issue on the other side.
I don't know if it's the chinese bulbs wearing the solder contact down, or the socket assembly itself.
Anyone have this issue and what did you do to fix it?
Usually if I reseat the bulb it works for a random while and than will break contact and stop working.
After dealing with this for way too long I need to find a permanent solution.
This is for my 95 wagon.