I'd use moly. It probably just needs to be cleaned out. The 9500 isn't waterproof, when you take it apart you'll probably find that out. I re-spool my cable once a season, that's normally enough to circulate the grease. Most people bolt on the winch and forget about it, they don't like that.I have a smittybilt xrc 9500. Not sure what differences there are between the x20.
It came with a sheet instructing the buyer to spool it out and pull it back in something like once a month. I didn't, and now it's nearly impossible to free spool. It feels like the grease in the planetary has turned into chewing gum so I'm in the process of researching what sort of grease I should replace it with to keep it from happening again.