Existing/imported posts not accepting images

Sorry for all the newbie questions, but, I’m having a hard time with adding in images to existing blog posts that were migrated. Upfront Builder is acting very twitchy. I’m double clicking to edit, once I’m in the blog element, it won’t give me an option for an image. Sometimes when I double click the entire post disappears or is replaced by the image I wanted to insert. Hope someone can help!