If the VH-11 hi-hat pad rotates on the stand, check the following:
- Stem tightness.
Make sure the stand's stem does not spin when the clutch assembly is turned. The stem should be tightened so that it cannot spin. - Clutch assembly.
Confirm the VH-11 clutch assembly is assembled correctly. The thumb screw on top of the pad, below the clutch, should be tightened firmly against the rubber washer (grommet). - HH cable.
The cable connecting to the underside of the pad also helps prevent rotation. With the pad in the open position (pedal released), take up any slack in the cable and secure it to the hihat stand with a tie-wrap, leaving just enough length for the pad to move freely up and down.
For details on correct VH-11 assembly and setup, see the VH-11 owner's manual: https://www.roland.com/global/support/by_product/vh-11/owners_manuals/