Problem with editor

hello,
I’m having issues with the editor. just to be sure, all other plugins are disabled, using a default theme, latest versions on everything. tried with different browsers, computers, cache is cleared. etc. tried just about everything.

On one of my test newsletters, when I try to add a new column, it adds the column with data from a previously deleted column, I can’t seem to add a new blank column without this data.

I have created a youtube video to show the issue.