Kitchen table swivel mechanism

[aframent]

I have a kitchen table that needs to be turned when we travel. The swivel mechanism locked up on our last trip. The metal locking plate is turning. Has anyone else had this problem. Looks like I can unbolt the table top. There’s a nut and a single threaded post in the center. Seems like the metal plate is not secured to the square table post. Do I take the nut off to get to the metal locking plate?
Thanks for the help.

[JRTJH]

Im not a fan of working upside down, on my back, so I'd turn the table over to make it easier to work on. The table is held to the slide floor with 4 bolts, one in each extension of the base. I'd remove those screws, turn the table over so you can easily access the mechanism, inspect it and determine how to best remove the wooden pedestal to access the metal base plate.