Hi, I have the same problems. Camera bought on aliexpress plaza spain, working now with a transcend premium 300x 32gb sdhc u1|
My firmware is 1.3.3 and I downgraded to 1.2.3 to try if the issues are solved without any result. Now I'm again on 1.3.3.
I bought a sandisk extreme u3 v30 64gb, it just worked 2 times during my tests. I tried all of the tricks I read on this forum. I tried both fat32 and exfat, different block sizes, 64 and 128, formatted with windows and osx. the sd card is very fast, but I get in the camera the famous "sd error". back to the computer, the sd is working perfect.
today I returned that sd to the shop, I don't want to spend money on a sd card I can't use, but I know the problem is not the card.
I tried a 64gb kingston sdxc u1 and it works at terrible speeds, the camera shows "slow sd card" message and when I finish recording a video, it spends a lot of time with shutter's red led blinking and a camera bussy message.
I'm in contact with xiaomi support...