66 Vibrolux Tube "socket"?? related noises

[TerryD]

The amp had been running pretty good for a little while.  Then I was getting some intermittent (major) distortion and intermittent loss of volume to almost nothing. I messed with some 12ax7s with my hand and it seems like that is the trouble. 
I tightened up all the tube sockets.  Got some DeOxit Dp5 and used a china tube to clean out the sockets.  It sounded tight and strong for a couple of days. Now the intermittent distortion and loss of volume is back.  If I jerk around with the phase inverter tube and the one next to it and push them in it plays good for a while. When I had the chassis out everything looked connected.
 
Any ideas how to resolve this problem??
I usually don't keep the 12ax7 metal tube holders on, as I think they make the sound a little metally.
 
Thanks, Terry