07-30-2018 08:47 PM
I'm having the same issue (long time to format, still showing error). How did SanDisk help you determine that they were fakes?
I was able to format my card on another camera (Canon SX280 HS) and also on the computer.
Well the problem was not my GoPro Hero 6. The problem was the Sandisk Extreme Pro 128gb cards I purchased on Amazon were fakes. I contacted Sandisk and they confirmed the cards were not authentic. I have returned them to Amazon and the new cards I purchased are working fine.