[bussard]

my feeder chain on the 7120 did the same thing, the chain jumped sproket a few times and then wore excessive, we replaced it at the end of the season, and could not find out why it happened, my guess is that under load the top large shaft with thesprokets on is flexing, and allowing chain to jump, and spring tensioners also help in the process, this was a new problem to the 20 series, and was modified from the older 10 series