I have this problem too.
But I often can’t even get to this stage at all. The photos on the Identify screen take ages to load. Then any obs opened in the modal that have more than one photo (and sometimes even only 1 photo), I get blue stripes to show there are more photos but they either take ages to load, or don’t load at all. The first (or only) photo often doesn’t load or half loads in which case the top half of the picture is there but the bottom half never appears (and there’s usually no organism in the top half).
If the photo does load and I click on enlarge, I often get the spinning wheel and nothing further happens at all. If it does eventually load, it usually takes ages.
I find iNaturalist to be extremely slow most of the time. I test other sites, and they all work fine, so it’s not my connection (which is slow, but fast enough to do everything else on the internet). There’s something really hogging resources on iNat or something. Often the page will load but all images just have a broken image icon (including avatars, thumbnails and images). Also, the text is all in bold until the last second when all becomes unbolded.
The places where loading mostly comes unstuck on iNat are goog maps, static.inaturalist, tiles.inaturalist.
I have just tested enlarge on the Identify page now, and it is taking around 80 seconds to load the image (after waiting a long time (didn’t measure) to load the page).