Using vinegar to decalcify I find it to be a waste of time
What I have found to work is using Cillit Bang Power Cleaner Limescale and Shine
To use - remove the hose attachment screw, the filter and the grey plastic insert
Insert a a small funnel into the centre of the housing and squirt the foam spray into the mechanism via the funnel (4 - 5 squirts). There is a little bit of wastage, but enough of the foam does go inside the mechanism. Reassemble the removed parts and make sure the hose connection screw is on firmly. Leave to stand for 24 hours. After 24 hours connect to the hose pipe and turn on the water You may need to initially manually rotate the mechanism a couple times and then hopefully it will work okay Depending on how badly calcified you sprinker was, you may need to repeat the above a second time. If it does work okay I would advise repeating the above operations every 2 - 3 months
Mine was calcified quite badly and is working fine now, hopefully you will have the same success
Regards Lenny