I once had shifting problems with an Ultegra RD. Unfortunately, I discovered this at the start of a 24-hour, 360k ride. Normally, I ran that setup (with bar-end shifters) in 8-speed index mode, but switched to friction when I realized indexing wasn’t working. Even in friction, however, shifts were really sloppy. After that ride, when I got around to trying to figure out what was wrong, I realized that I had switched the upper and lower pulleys when previously cleaning and reassembling the RD. Whoops! Not sure if this would be a problem for the DA RD, but it’s worth checking (on the Ultegra the pulleys are clearly marked, but I wasn’t paying attention).