My Di2 gears packed in due to extreme heat over in Mallorca one year, locking me in the 52/11…! I had to get from Over Murro back to Palma Nova I looked just like Olly on the flat, and i kind of got into it as you just batter on with what you’ve got Then came the climbs and the weaving around, just crazy and my legs were over due to explode and minute. I remembered a bike shop on the edge of Palma and begged them to help me out as bigger climbs were afoot to get home. They kindly stripped out the wires, found no faults, put it back together and it just started up working again!! Defo the heat i think. Got back home ok but it then packed up again a few days later. I cooled off the bike in an air conditioned sympathetic garage and hey presto it worked again!! It was around 34 degrees and would be hotter inside the frame i guess with the sun beating down. Have you ever had this with Di2? It was Dura ace 3rd gen woth the clever battery. Cheers.