I had similar problem in a Calidus recently. Compressor works but air doesn't come to cylinder. The reason was that some very small particle blocked the jet which regulates airflow speed to cylinder. This particle could be a result of oxidizing inside pneumo system. Disassembled, purged off with air pump, works now.Any one had the compressed air to the Prerotator piston just stop flowing. All other pneumatic funtions like rotor brake still work.