Reduced image resolution on published site vs designer

I’m getting substantially reduced image resolution on my published site versus when using the designer and I have no idea why. I’d prefer not to share a link at this stage but if anyone can suggest potential causes for me to troubleshoot that would be very helpful. Is there any way to force higher res?

Here are two screenshots, the low res one is from the published site and the good one is the same image viewed in the designer:
published designer