C61W-700 mini not responding correctly

My system consists of a Genie 2 HS17-500 and 2 C61W-700 mini receivers. One upstairs in a living room and one downstairs in a TV room. The mini receiver upstairs is not responsive to the fast forward and rewind feature on the remote. Sometimes it will work but it's very sluggish when it does. The one downstairs works flawlessly. A few  details.  The upstairs mini is on the same floor as the HS17 tower and is in direct sight of it. The mini that is not working is approximately 10 ft. from the viewing position and there is nothing between the remote and the mini. The first thing I did was replace the batteries in the remote. When that didn't resolve the issue I purchased a new remote but the problem still persists. The mini downstairs that works fine is about the same distance away from the seating position  but is actually behind some other audio equipment and not even in the line of sight of the remote. Does anyone have any idea what could be going on here?