Just did a segment this evening. From the moment the segment started to the end of the segment there was no power-data recorded (the datafield for the powermeter also only showed 0W). Cadence (also coming from the PM) was recorded without problems. After I finished the segment the powermeter showed normal values again.
So I guess it must be a software bug (bug reports in the beta section are already closed). I checked the data also on Strava: power failed exactly during the segment (took me about 14min) and is flawless before and after.
the PM is a P2M NGEco if that matters.