The vulcan bars are slipping a bit. I have had similar problems with powdercoated bars before. I should have used knurled bars or at least bars that weren't squared off because the last guy tried to 7/8 clamps on a 1 inch bars, but no matter.
First cover the tank.
Mark the bar so I know where I want them.
Take off the top clamp.
The powder has ground off a bit and is basically lubricated the clamp and bar joint.
Rough up everything with some sandpaper.
Clean everything with alcohol.
Somewhere between red loctite and JB weld is green loctite.
I just put a bit of this on all the high spots, i.e. the shiny spots.
Clamp and torque. If that doesn't work I'll have to get a new knurled set of bars.