Not sure if anyone else has this problem but when I go quickly down a rough downhill section of trail, I go to pedal at the bottom and the chain has jumped from the middle ring down to the granny and occasionally jumps off the front rings all together. This seems to happen about 50% of the time and is now getting quite irritating. Is there something I can do to stop the happening? The chain and cassette are slightly worn now but they have done this from new, I upgraded to a better chain than originally on the bike, to no avail.
I have a Deore Crank set, X7 front derailleur and Sram 991 chain. I also have Sram X9 rear derailleur if that makes any difference.
Thanks in advance for your help.
Edit:- It's a 26" HT 3x9