List of steps to reproduce (step by step, including full links if applicable):
open a page in edit mode in en.wikisource
https://en.wikisource.org/w/index.php?title=Page:The_White_Slave,_or_Memoirs_of_a_Fugitive.djvu/386&action=edit
or in fr.wikisource
https://fr.wikisource.org/w/index.php?title=Page:Zola_-_Madeleine_F%C3%A9rat,_1869.djvu/92&action=edit
point to the image scan, and click to scroll the image with the mouse middle button.
What happens?:
the image changes size + - whether it's in over under or side by side mode.
What should have happened instead?:
the page to scroll vertically, and the second mouse click activate the image size - as it used to be.
Clicks to change the scroll button assignment are not working
Software version (if not a Wikimedia wiki), browser information, screenshots, other information, etc:
Windows 10, Firefox 94.0.2, & Linux Mint Firefox 94.0.2
Windows 10, Chromium 96.0.4664.45 Linux Mint Chromium 96.0.4664.45