When running in the middle ring if I select one of the two largest sprockets, the chain automatically changes to the smallest ring. Why is that happening?
Your FD cable tension might be a bit loose. If you're using trigger shifters, does it hesitate to shift from the small to middle ring? Also check the alignment of the cage plates to the chainrings. They should be parallel.
The trouble with common sense is it is no longer common
Check the alignment and height of the front Der. The front Der normal runs parrallel to the main axis if the bike, sometimes the move a bit.
Sometimes it needs to be just a littl off the axis to improve shifting one way or the other.
Notice the bumps of the front der chainplates, watch what happens has you shift.