Looks like its a AVIF image. AVIF is not well supported unfortunately. Even on the latest version of Android it’s not 100%. But support is significantly worse on older versions of Android.
It works fine in the browser because browsers bundle their own AVIF decoders.
This post looks like this on my client lol (its normal on the browser)

Summit user here, I thought this was some sort of acid trip post.
Looks like its a AVIF image. AVIF is not well supported unfortunately. Even on the latest version of Android it’s not 100%. But support is significantly worse on older versions of Android.
It works fine in the browser because browsers bundle their own AVIF decoders.
Support will gradually get better over time.
ohh i see,ty.
Boost? I have the same issue. Lots of image viewed from Boost have a tiny green line on top too.
raccoon, it only shows for this post.
To be fair, that is pretty hard to understand.
true