Swivel seat wobbles?

[PDXDave-SMB]

So I have the typical fixed base drivers seat and swivel base passenger seat.
We've fitted Scheel-Mann seats as the OEM balance balls were flat horrible.
The drivers seat is solid as an anvil and doesn't wiggle a bit.
The passenger seat is a wobbly mess, and was prior to the seat upgrade.
It's primarily an issue on any road that not a sheet of glass and makes my wife nuts with the constant fore-aft wiggle.
I've disassembled the swivel base and checked for broken, loose or otherwise problematic parts, finding none.
When I reassembled it, I greased everything and torqued the castle nut to what felt a "proper" 55# feet. It's as tight as I care to make it and is still wobbly.
I've diagnosed it thoroughly and there's NO doubt that the movement is in the swivel base.

Has anyone managed to cure this?

 

[bigriver-SMB]

Check for play in the swivel latch mechanism. That's where my same problem was. I had a local welder fix it.

 

[86Scotty]

Is this a seat base from Ray/1der or a Sportsmobile original, or unknown?

 

[mgmetalworks]

I've had play in the seat slides Scheel-Mann provided before. Are they still tight?