Spinaflo cara?

Spinaflo cara Caravan Hob propane / butane gas hob 5 taps.
5 gas tops on the cooker hob 2 work 3 don't been unused since Oct last year wintered at home.
Each of the three none workers had white furry deposits around them the two workers didn't. Can't say its a leak as the dial on the cylinder which was turned off still showed green indication no leak of gas left in pipe. They can't be depressed off the 'Lock off ' safety feature and this of course prevents turning them on. Any suggestions in freeing have tried wd40 puddle in plasticine around each tap for 18hrs not a movement. Tried gently tapping protecting shafts with piece of wood, still no movement. Any suggestions I would be grateful.

Many thanks