In the new editor if you copy anything and paste, all the text is put like one tab maybe to the right? This breaks all lists and headlines that have to be manually fixed, which isn't hard just have to deleate the "tabs", but it's very annoying in a long article. Also tables compeltely break when you copy them (And as a side note could you please look into the tables they are kind of buggy in general). This whole thing wasn't an issue before with the new editor but has suddenly come up like in the last few weeks or so.
Copy anything from the new editor and paste it into the new editor.
Editing text in the new browser editor.
I've been working on the fix for the couple of weeks (same with mentions being cut off when you try to copy and paste them somewhere) and probably it'll go live in the next couple of days - thanks for reporting