I have one of them and I pulled the drive wheel lately. It was tricky but not really too hard to get it back on right, with the nut tight and minimal end play on the shaft. It could be the drive wheel is on too tight now. Adding oil can be a problem due to some oils get gummy. If you do get it apart, perhaps you should just wipe every thing down and use the absolute minimum of new lube. I hope someone can chime in on good/bad lubes. I would NOT use WD-40 in here!.

But mine works well without adding lube.