My blog site has seen upgrades from RW 4 to 5 to 6 to 7. I’ve been using it for years. I’m on 7.3.1 now. I’ve never seen this problem before. I have hundreds of blog posts with a ton of images. Suddenly, a lot of the images randomly have been resized. I always make my images 620 pixels wide. Here’s one for example. It’s suddenly been resized down to a tiny image.
Here’s what it looks like in Edit mode. My 620 pixel wide image is now a tiny thumbnail.