Now that we understand what the issue is, the tube is turning, I think it will be simple from here on out. I just looked at my bike. The pinch bolts (#4) are readily easy to see and touch on the boss, just inboard and slightly up from your problem bolt. Assuming they are both there, tighten them with an allen wrench. See photo below by poorly drawn feeble red arrows.
If those bolts are missing - 2 of them - #4 in the diagram - then have a helper hold your problem bolt while you put back and tighten the bolt on the other side. This should hold the tube while you take out the problem bolt.
If that fails, look at the tube. There is a flat ground on the tube about 2" of the way from the left side. . This flat is there to hold the tube with an open end wrench as needed.
Got it Paul. I did feel the flat ground on the left side of the tube and it should be fairly easy to get an open end wrench on it. hanks again for all of your help.