Quote from: roofusj on February 10, 2020, 08:52:08 AMJust about a week ago I tried Lexar (I think it was 1800x or something very similar to yours) and experienced exactly the same behavior.
I'm using a Lexar 1667x 64 gb V60 card and i have similar behaviors from it. At first it won't record more than 3 or so seconds in 5k rewire mode. Then after 3 or 4 failed attempts it starts recording just fine and as long as i don't turn it off it will keep going like a champ almost getting to 60 MB/s with constant recording. It works fine in mcm rewire.
A bit of remedy was to use "Warm up card" option in menu. I think 256MB size worked for me.
It improved the issue a lot, but occasionally the card was still not able to start recording at higher speed. Also boot up time was much longer due to "Warm up" setting.
I also tried Samsung Evo with very similar issues.
Eventually I returned the card and ordered Sandisk Extreme Pro 128GB. Never had the issue since.
On a side note. It seems to me in 5K mode, 12 bit changes resolution. 14 or 10bits have different one. Is it a bug or I'm still missing something after reading this whole thread.