Diagnosis
Worn-out valve stem detents or a broken knob insert. The knobs push onto splined valve stems, and a plastic piece inside the knob provides the clicking resistance.
How to Fix It
Replace the affected knobs.
1. Pull the loose knob straight off the valve stem.
2. Inspect the plastic insert inside the knob. If it's cracked or the splines are worn, the knob is the issue.
3. Order and install exact replacement knobs for this model. Push them firmly onto the stems until they seat.
If That Didn't Work
The problem could be the valve stem itself is worn or damaged. This is less likely than knob wear, but if a new knob is still loose, the entire valve assembly behind the control panel may need replacement.
Heads Up
Don't try to repair the plastic insert with glue—it's a safety component that ensures positive on/off positioning. Using a damaged knob can lead to the gas not turning off completely.