I have a new SRM with powercontrol 5. I rode it in a half iron man tri on the weekend, only the third ride with it on this bike since mounting it, but it has seemed to work fine up until race day. Slope and offset were correct, I checked and double checked the offset before and after the race and it was stable. The problem is that the power numbers seemed kind of high to begin with and just kept drifting higher and higher, to the point where the computer was showing several hundred watts above what I was riding. The numbers weren't erratic, the relative range seemed normal, everything was just skewed too high and gradually going higher. It was a 4 lap race and I showed 310 watts for the first lap and 560 for the last one. I know I was actually riding about 250 at a consistent pace.
I've used the same PC V on my road bike's srm set up without problems and set the slope from the srm win software to match what's on my tt bike's cranks. I hope it's user error and that someone can straighten it out for me, thanks.