You didn't mention the rectifier you're using. I had wobble with my big bottles because the bases overlapped the socket mounting screws. Rather than take those out, bevel the holes, and change out to recessed screws, I added some felt pads for the tubes to sit on.
Just felt peel 'n stick pads you can get from the local hardware, cut in half so they're more or less hidden under the bases ...
And ya ... if you do a lot of rolling, it's possible the socket has loosened up. Wouldn't hurt to retension it - if nothing else, that will ensure good electrical contact, but ...
The pin connectors in the sockets provided with the kits DO float quite a bit, which I expect might be what you're experiencing. I suppose there's some way to tighten those up - some sort of flaring tool to push the bottom of the connection tight to the holes? Thing is, as long as you've got good electrical contact, and they don't move around if you're not pushing them, well ... don't do that.
PS ... I prefer a wooden toothpick to most anything else for shrinking the connectors if they're loose on the tube pins. Nice taper and minimal chance of going overboard and damaging things. And also, the connectors won't normally loosen up much if you keep the tube straight and apply even pressure to remove or seat it. Rocking it, or maybe trying to push it into the transformer for instance (;-) - that's what loosens them up. So, ya ... I'd think yours might need some attention.
Oh. Just a thought ... the rectifier would be the most prone to this rocking thing as it has fewer connections than the power tubes. All the extra solid wire connections tend to stabilize those better? Anyway, do the diode mod, and that gives you two less loose pins floating. Also a good idea to protect the amp.
Also, a slight twist of the solder tabs will help lock them in place. As you can see in the pic, I usually fold mine back just a bit - accomplishes the same thing.