I have the same problem within the same conditions. I can sort photos when adding a gallery to a page. But after saving a page there are no photos shown when I want to sort them again.
Hello. Same problem here. As a source is selected a gallery, but the “Sort or exclude image” just show “No entities to display for this source”. It worked properly in past.
Well, I tried to disable all of plugins – one by one, but it seems there is no conflict as the bug remains. I’ve rather disabled Onesignal plugin and switched to direct code insertion :/