I find that after I get a power dropout (or after I don't use the pedals for a while), that the specified crank length resets to 144.5mm, down from 172.5. This seems to reduce the reported power. Anyone else have this problem?
This problem is due to the 800 not having the right cranklength setting in one of its bike profiles... First, make sure your Edge 800 has up to date firmware on it. If you change the bike profile settings (or add one) then the 800 will not necessarily initialize the crank length properly. So you should go through your bike profile settings on the 800 and make sure the crank length is correct for any profile that includes the pedals as the power meter.