Auto-night mode doesn't switch back to light theme
Auto-night mode does not work as intended when set to either system default, or adaptive, or schduled by time, or scheduled by sunrise/sunset time. In both cases Telegram switch to dark mode, following…
1. The colorspace tags are being stripped from the video, causing it to be displayed in the wrong colorspace. Non-HDR colorspaces are understandably the default.
2. When displaying the video, no colorspace conversion is performed to display it correctly.
Since we can clearly see a difference in colors from just the thumbnail of the two samples you uploaded, I'm assuming the former is what's happening and the colorspace metadata is getting stripped from the files.
This leads me to suspect another similar bug that is much more subtle: video files that are encoded as bt709 or bt601 are likely having that data stripped as well, causing their colors to be interpreted as one or the other (depending on device and sometimes even the video resolution). This can cause reds to be slightly more orange, or slightly more magenta, than they should be (depending on which standard it's encoded as, and which standard it's decoded as).
So basically the fix for that "bug" would be to implement something like ffmpeg to handle pretty much any type of media.