[DeckApe]

The lighter tan socket is indeed the culprit, and I thought it looked lower in quality.

Actually, the keyhole survived. It's the little chunk of bar that holds the #6 pin in place. A closer inspection reveals that the socket has warped slightly and allowed almost all the pin sockets to come loose, so I suspect replacing the socket is overall a better idea for future generations (or even in a couple of weeks when I try to put the tube back).

Where the heck do I get a replacement socket? I looked around on line and found loads of loctals and large-pin 8's, but I couldn't find a small-pin 8 anywhere (it doesn't help that sellers seldom include a flat picture of the socket so you can actually get a good look at the pin configuration).