html code repeats itself endlessly

When I look at the html code of my pages, I see that some code is repeated dozens of times, especially the command. It looks like this:

What could cause that? I keep deleting all the superfluous code, but it keeps coming back. This only happens on pages where I do a lot of editing and changing.

My second issue is that many times when I try to create an empty line between a graphic or video and the text below by hitting the “enter” key, when I update the page, the empty line disappears. My workaround has been to enter a period in the empty line and that makes it show up. But there must be a better way than that.