Many of my posts have embedded images. When I view the posts individually, sometimes these display as thumbnails and sometimes they're full-size. Sometimes I can view a post and see that the images are full-size, then come back a few minutes later and find that they've been reduced to thumbnails! It's an art blog, so I'd prefer that they be full-size, but the most annoying thing is the inconsistency.
Is there a setting I can change to stop this from switching back and forth? The theme I'm using is Visual.