Problem when uploading horizontal video to Instagram

Hi there. I’ve been having a problem when trying to upload a video to Instagram. As you probably know, the platform cuts your posts squared-shaped by default. My video has a 1920x1080 resolution, so it gets cropped as expected. But apart from that, it looks right.

The problem appears when I try to adapt it to its actual aspect ratio with the “<>” option at the bottom left of the screen when selecting it from your gallery. It gets adjusted, sure, and looks fine while you are preparing your post… Until it gets finally uploaded and pops into your feed with some nasty colour bands and distorsion onto it.

Normal image:

Image as seen in the Instagram video:

I thought it could be some compression/codec-related issue, but I’ve tried to use different encoding settings and the problem remains exactly the same, or the platform doesn’t accept it at all. It happens both when uploading it from within Instagram and when sending it to upload directly from your gallery. It happens both when you upload it alone and when you upload it along with other content. Sound is OK, at least.

Does someone know what is happening? I have not found anything about this issue on the net.