Published Desktop Layout Loading Mobile CSS?

I’m working on optimizing my layout for mobile — upon publishing and refreshing the page after some edits in the mobile test view, I’m encountering a completely broken desktop layout. It appears to be loading the mobile breakpoint styles…?

Any guidance on why this is happening and how to correct?

Here’s the layout:

UPDATE: It happened again! This time I went to save the template for use on another page and it completely jacked up my homepage layout. Below is the layout before saving the layout template…