I have adjusted my limit screws on my rear derailleur and it seems to be indexing correctly, however, ONLY when I pedal backward and freewheel the chain skips to another cog. It happens mainly when I have it on a stand and I freewheel while putting lube on my chain. What would cause this to happen? I am not putting any pressure on the chain or derailleur when applying the lube. I have tried adjusting the barrel adjuster and the limit screws without much success. It seemed to work for a limited time but after about 5-6 rides it skips again. If this is happening, does it mean I have not adjusted it correctly? Any opinions would be appreciated.