Originally Posted by NoRacer
IMHO, it sounds like you may be on the edge of a misadjusted RD cable. It may be happening over time because of the flexing of the frame while riding.
Try tweaking the barrel adjuster.
Thanks. Aside using sight to make sure the top RD pulley is directly underneath the cogs, any other way to check if the RD cable is properly adjusted? Also, if the frame is flexing will this help?