Extensions and Ys tend to get corroded after sitting around a while. I have had too many problems with Ys and never use them. Because I'm too lazy to be bothered cleaning wire plugs I solder in my own wire extensions. Try shooting some electrical terminal cleaner into your plugs and pull them apart and put them back together 10 times then try it again. Just sounds like dirty ends. Another sign o dirty leads is slow moving servos. Just an FYI.