Thanks, Jeremy. Good to know.
Another similar bug is a Javascript error. Sometimes, when I write a filter and forget to open or close a "[]" pair, there is a big red error message that pops up every time I push any button, even when the error is already corrected. I believe, the problem is that the error is corrected in the "Draft of 'Tiddler'" rather than in the 'Tiddler'. The workaround for me is to save the file saving "Draft of 'Tiddler'", then opening the file again, opening "Draft of 'Tiddler'" and renaming it to "Tiddler". This also seems to be incorrect behavior.