This was an odd one. We lockout navigation after the user makes changes on some views until it is saved, this entails disabling several dropdown components on the page. After lockout, the user can click on the locked down dropdowns to open a pop-up to unlock navigation and abandon their changes, this uses an on-click scripting event that opens a pop-up. In 8.1.11 this works fine, however in 8.1.12, after some investigation I found that if you disable a dropdown component and then a scripting event on that dropdown is activated, the dropdown becomes permanently disabled. I tried it on a few other components, but it appears to only occur with dropdowns.
I presume this is an unintended bug.