Yes, I have. I have no issues with JPGs or PNGs but any other format is a gamble. If you have a recent post you can get to to check, maybe you can add what format that image was (or add the link to the post with the image if you're okay with that)?
Boost for Lemmy
Community of the Android app Boost for Lemmy

It might be my instance issue then. There seems to be some image proxy being used. Maybe it messes up the format the app deduces…
Lets see how this works, it doesn't open for me.
It's working for me. Can you link to the post instead of the picture?
It's basically every post. I posted a link to the image, because my instance has this image proxy so all images seem to go through that. It seemed more relevant.
EDIT:
I just found an image that works. Those are rare tho… Here's the link.
I also have that problem. I find clicking the link icon on the bottom usually displays the image as a workaround
I've found that to work as well. Recently it feels like there's way more such images.
It's all those avif images on your instance.