Steps to reproduce
- Go to https://test.wikipedia.org/wiki/Ji%C5%99%C3%AD_z_Pod%C4%9Bbrad or https://cs.wikipedia.org/wiki/Ji%C5%99%C3%AD_z_Pod%C4%9Bbrad
- Scroll down and open an image with mediaviewer enabled
- Close mediaviewer (reproduced only with esc pressed, but that might be just a coincidence)
- If browser didn't scroll up, try again
This appears to always happen in Firefox >= 70 and sometimes happen in Chrome. These may be two different problems, but may have the same solution.
see https://martin.urbanec.cz/files/screencasts/T229484.webm for screencast