Back in March, I had my Rival group replaced with Ultegra Di2 and I'm very happy I did.
A few weeks ago I started to have a problems with some gear slipping. Basically, it wouldn't stay in a certain gear, and the problem wasn't consistent. Then it got worse; I was doing some hill repeats and the RD wouldn't stay in the biggest cog.
I took it back to the LBS, but the lead mechanic wasn't in and the other guys said that they don't touch Di2. It did jog my memory that the lead mechanic did show me how to make small adjustments to the RD. The Shimano written instructions didn't say anything about it, but Google came through (push and hold the battery check button and then hit the right shift buttons to adjust the RD up or down).
What's odd is that as soon as the five seconds were up, the RD starting moving up to the big cog and the light went out. I was turning the crank all this time. I never did get a chance to hit the shift buttons.
The positive slant on this is that the problem went away. So, when the RD started marching up the cassette it seems to have fixed itself. Is this normal behavior?