It’s not ideal. I spent some three years looking at Openrent ads without thinking to click to enlarge the picture (why would anyone click twice on a picture?!) I expect many prospective tenants did the same, just seeing the floor of my lovely lounge rather than the whole room!
Pictures do show better on Rightmove and Zoopla, as per the response you’ve seen, however I would have thought many prospective tenants look at the Openrent portal.
One thing I spent a long time doing was resize a number of my images to make them “fit” on Openrent. Don’t do this as they then look odd on the other portals!
I’ve asked Openrent about this a few times, I don’t really know why they haven’t fixed it. The response below is familiar - “it isn’t a cause for concern” when you have raised it as a cause for concern. A denial there is a problem at all means it won’t be fixed anytime soon. Sorry I can’t help more.
Good luck with your ad!