I am using Pocophone F1 (MIUI Global Stable I have experienced a bug where the audio starts only 3-4 seconds later then the video. This is hurrendous for smaller videos which are about 10 - 12 seconds long. It even happens on videos, that are larger in size and length (01:30 and about 25MB in size). After a while, the video lowers it's frame rate to re-sync with the audio.
I have experienced similar behavior on a older phone like Redmi 3s Prime (MIUI Global

Could it be a problem with the video files or could it be the software? If I can fix it, how can I do it?

a loyal Xiaomi user.