I haven't tried to reproduce this.
I copied a page title from Meta and pasted it into VisualEditor on another wiki. The text was set to =Page title= and highlighted in very pale blue, with a dashed line underneath, so I set it to Paragraph (that worked) and went to the character formatting menu to clear the formatting. The 'Language' item was highlighted, so I chose that.
The first time, the dialog box that popped up was tiny. It was barely big enough to display the "done" button, which was overlapping with an odd "$1 AUTO" string in gray text.
The second time, the dialog box looked normal, but 'Remove' didn't actually remove anything. 'Clear formatting' also doesn't remove anything.
Then the box got stuck open. It would go away if I highlighted text, but 'Done' didn't close it and clicking outside it didn't close it.
I was able to keep editing and to save the page when I was finished, but it produced <span dir="auto"> tags, which I didn't want.