A common occurrence when using the PC-7200 piston-cylinders (liquid lubricated, gas operated piston-cylinders) is having the lubricating oil splash onto the upper and lower end of travel stops. This causes the piston to stick when it begins to lift off from the lower stop position or when it begins to drop off from the upper. The critical surfaces of the piston-cylinder are clean and that is not the problem. The problem is with the oil film which as formed between the end of travel stop and the piston head, forming weak seal.
When operating with an Auto-Float ("AutoGEN") system the weak oil seal can cause difficulties bringing the piston into float. The symptom is most often seen as the AutoGEN controller brings the pressure past the float point, the weak force of the seal is broken, and then the piston over/under shoots to the other end of travel. This cycle repeats itself.
The solution is to clean the film of oil from the end of travel stops. This video shows how to do it.