Roll back the accessibility UI update by default, and add a toggle to enable/disable it in the Dashboard settings page
< Feedback em Tumblr Accessibility UI Update Toggle (Defunct)
Uninstall it, the replacement is being worked on but won't be a user script.
Broken Script
Every time I load a page on tumblr I get a popup for the script not working and to wait for an update except this has been happening for months and I can't figure out how to get it to stop. Even updating it doesn't help!