So from what i am understanding... you never tried tightening it even once right???
You should get it tightened so that you can exclude one cause that it isn't loose. Fearing that it may jam??? that's no problem, you can loosen it if it happens. what to fear???
Take a 17 size paana and a paichkas.
Use paana to unscrew this main bolt. Loosen it to the extent that you can rotate it with your hand.
Notice this ring under it.
Set paichkas in that groove and tighten the ring by tapping the paichkas at the other end. You can tap just with your hand with force, if it is loose it will move and once tightened it will stop. You can't over tight it just by tapping with your hand so don't worry about it.
Once this ring is tightened, use your pana to tighten the main bolt back to its original setting. That's it.
Do it, and if this doesn't work then work your way to find some other cause.