Just an update, a year later I am still having this same issue and have sent my camera in for Canon to repair it twice and I am STILL HAVING THE ISSUE. Beyond frustrated at this point. Now it happens to mine even with 64 GB cards, brand new cards, ...
Does the second slot work well enough for it to function? I have a back to back sessions over the next month and don't really have time to send it off to Canon yet. Right now it's working ok with a handful of cards, but worried it will give out on ...
I started having this same exact issue this week with my R6 mark I. Did you ever come to a conclusion or a solution for 128 GB cards? Did all new cards work?
