OnePlus 3t Video recordings turn out to be only 1 second long

[AC Question]

Recently i went on a trip in Africa and used my 3t to shoot a few video clips at 4k resolution. Everything felt right at the moment, I started and stopped the recordings for around 1 to 2 minutes, no error messages or anything. To my great surprise, at the evening, when I tried to playback these clips, they were only 1 second long. Tried to google the problem, but it seems it hasn't been discussed so far. Does anyone have a clue what may be causing this issue? I had the device since December and this has never happened before. Also, I am doing some tests now and everything works well, but I feel I cannot trust this camera anymore to capture important moments..