HumansCanWinElves wrote:
Indeed, I see the problem, and has encoutered it before.
As a temporary solution - when I click the EDIT SOURCE on the dropdown of the EDIT button, it seems to show up well and to remain even when switching to the visual mode.
At the same time, I would recommend you to report this as a bug through the official form Special:Contact, and also to put it on the unofficial document for tracking UCP problems User:Noreplyz/UCP.
By clicking edit source, it won't bug out, but when I click the drop down and change it to visual editor, it will all delete again. I'll just use source editor from now on. Thanks for your help!