Even after a battery change (both pedals with new batteries) this error happened so i dont think this is related to batteries.
But i did few tests today and i found a solution which i s working for me... When i turn on my Edge, and spin my pedals with my hand to wake them up - then i wait like 10 sec and spin them again few times and wait few more seconds... And then the calibration proces went well on first try... It looks like the one pedal needs more time to "wake up" and when you click on the calibrate straight after the Edge prompts... if fails with this 1280/1285 error.
