I believe this is a side affect of the media loading optimization I had mentioned in one of your previous posts about background refresh. It could also be that the image failed to load during the first request, and succeeded the second time when opening the post. I’d assume if you scrolled that post off screen and scrolled back, it would show the image.
I have a few ideas for how to fix this, as I have seen it happen a few times. I’m hesitant to add support for retrying network requests for loading media, as it can impact performance. I may try it out though and see how it holds up. If not, I think I’ll add a message to the image view explaining that the media failed to load, with a button to retry, or open in the browser.