I’ve been using the Manfrotto 410 geared head for some time and it’s been a great compact unit, but recently one of the knobs has been loose. It started happening when I used the head with a video slider which put a lot of cantilevered pressure on the head. I thought I had broken something and put up with a bit of play in the knob before it engaged. Last week though it got to a point where it would only turn in one direction so I was forced to pull it apart and I realised there was a simple adjustment screw for tightening each knob.
What you need to do is pull off the rubber cover of the knob and underneath you’ll find an alan key screw. Tighten that and you’re done. Also worth putting that alan key in your camera bag because when you’re out in the middle of no where it can be a pain in the ass trying to hunt one down.