- go to http://en.wikipedia.beta.wmflabs.org/wiki/Language_Screenshot?vehidebetadialog=true&veaction=edit
- click insert > more > special character
- the insert special character popup window appears for a fraction of second and then disappears
- for the video that reproduces the problem see https://saucelabs.com/tests/db861630daca43eaad105b72e8e28963
- reproduced on the latest versions of chrome and firefox