Edited photos show original version when expanded

I own an iPhone XS running on iOS 12.0.1. When looking at the photos taken and edited on my phone (unzoomed) the images display the changes I've made on them, but when I expand them by clicking on any of the photos, I get the original version. If I then click edit, it's as if the picture had never been edited at all. I go back to the main photo collections and the pictures still looked like the edited version.

Does anyone else have this problem? Any suggestions on how to fix it?

Thanks in advance!