
I was able to transfer about 25GB of .mpg files (video) to the card and then as I added more, the files began to disappear or be corrupt. Sometimes whole folders are gone. It didn't matter whether I transferred to my tablet via USB cable or used an SD adapter on my main computer. The card was wrong. I bought a different brand card and had no problems.

π½ 512GB Samsung Evo Plus Micro SDXC Memory Card
40 Review

SmartBuy Classic Series microSDHC 32 GB Class 10, R/W 25/30 MB/s, SD adapter
41 Review

Memory card Samsung microSDXC 256 GB Class 10, V30, A2, UHS-I U3, R 130 MB/s, adapter to SD
50 Review

Kingston microSDXC 64GB Class 10, V10, A1, UHS-I U1, R 100MB/s Memory Card, SD Adapter, 1 pc, Black
45 Review