When I paste in a 1700+ line HTML file into the web editor (raw HTML mode) and hit Save, the page does save appropriately, but when the page reloads the editor truncates the text.
So if I were to keep editing, then save again, I would be saving an incomplete page (and I would lose whatever was there before).
Current workaround is to always paste the entire page (from the source on my machine) then hit Save.
Here’s a screenshot of where the code was truncated. That’s line 1137 out of about 1700.