If your bonnet is actually moving there are rubber adjusters that you can manipulate to make it settle. Slip your fingers under the gap as much as you can and see if you can lift it or press it - if it moves, adjust the rubber stoppers by twisting them. Usually, anticlockwise makes them lower, clockwise makes them higher - but haven't done this on the D22.
If the bonnet latch isn't being held low enough, you could try moving the striker plate downwards (I'm not even sure if the D22's is adjustable). Check for damage in the cross member too - it might need a panel shop's attention. If there is damage and it lets go at high speed, it's very, very dangerous.
Edit: if it's moving in relation to the bullbar ONLY, then it might be cabin movement and a trick of the eyes. You might check your cabin (body) mounts to make sure they're not loose, but other than that don't worry too much!