It’s a real shame, as I really like using Raw Power otherwise, and I much prefer how it handles non-destructive editing files so much better than anything else (Pixelmator Photo, for example, can create huge sidecar files, into the 10x original kind of scale). Of course there are other features that are good too, along with its general capabilities for editing a photo.
As it is, I have just switched to using Photos itself for the bulk of my editing, and find it’s not really doing a bad job. The others I always had available there, but used them for different purposes. Most annoying is that not one of them has all the tools one might need when editing on an iPad – Photos is the only app with Red-Eye repair, Pixelmator is the only one with a Repair tool, and Raw Power is the only one with a proper non-destructive workflow that works with a Photos library.
I’m guessing there’s just something screwy going on with rendering a preview image somewhere, but I can’t see anything on an iPad that might improve it (like you could get a corrupt colour profile in MacOS, and just switch to a new one).
Cheers, and all the best