We have a john Deere 843 corn head and one of the rows we are having an issue with and wondered if we could get some input? When we started the year everything was fine, then it threw the gathering chain a few times and we noticed that it was missing the snap ring and we fixed that and changed the chain thinking it was slightly worn. We haven't had any issues with it until running the other night it seems to have grenaded. It threw the chain and noticed that it was slightly warm; upon further investigation the sprocket and its shaft move up and down/wiggle. Is there a certain thing that would cause this? I have the parts diagram and list from john Deere and was just wondering if there was something to look for specifically or if need to disassemble and rebuild everything? Thanks for the help.