A week ago my right DA shifter began to shift poorly. When shifting to larger cogs, the first shift takes very little pressure, but doing multiple shifts, the shifter makes a horrible grinding noise and typically puts the derailleur between cogs. This continued for an entire ride, while I adjusted the cable tension a little during the ride. The following ride there were no issues. The next ride, after not touching the any part of the shifting system, the grinding in the shifter became worse. The cables and wires don't have too many miles on them, could this be a problem with the shifters internals? Thanks.