Originally Posted by
joejack951
What shifters again? (maybe I missed this earlier)
Have you tried a new middle ring/crankset? A heavily worn middle ring could want to hang onto the chain enough so that it won't easily derail down to the granny. Clear, close-up pics of the area could help this diagnosis.
Shimano Deore XT SL-M700 Deerhead thumbies
That was my next thought - to replace the middle chainring.