So I just picked up an LTE Surface 3 from AT&T and so far, I'm loving it. However, I've had one issue with the micro SD cart slot. I took the 64 GB card that I had been using without issue in my Lumina 2520 tablet and placed it in this one. At first, it didn't see it so I reinserted it. It saw it and I started playing a movie off of it. Shortly into the movie, playback stopped and I received a message saying that the file could no longer be found. I browsed back to My Computer and noticed that the card wasn't showing anymore. I reinserted it and showed up again and I was able to play the whole movie. However, this kind of issue has been repeating. It seems nearly every time I need to access the SD card, I have to reinsert it and the amount of time it's visible varies. The card worked fine in my Lumina 2520 so I'm thinking it may be the Surface? If anyone has any thoughts, please let me know.