Bike rack arm removal

[Trouge]

Hi Guys, I’ve tried searching but can’t find how to remove the arms on a genuine VW cycle carrier? The knobs unscrew but don’t open the jaws wide enough on the clamps and it stops turning before opening. I’d like to remove the arms, dismantle and lube to see if I can fix. Failing that I’ll have to buy new arms. An instruction manual or idiot guide would be much appreciated. TIA.