i'd be checking the Derailleur hanger first. and then looking for a twisted or Worn Out/loose Derailleur... the SRAM products i've had similar issues with seem to be extremely loose in the pivot pins... i mostly see the MTB lines, but still.. Look for slop in the Derailleur. Shot pulleys/bushings have been found too.
a worn chain can also cause really annoying, changing shift hassles.... side-to-side, wet noodle wear, not length wear.
none of what you list as symptoms points to cabling...

and, there's a chance you've run into a mismatch between the shifter and derailleur... SRAM just loves re-inventing the wheel for no reason whatsoever....
what exact models of the der. and shifter are you fighting?

personally, i advise against using SRAM derailleurs and shifters.... others seem to stick by it even while they cuss at it.