Just a heads up to anyone thinking about updating to 12.1.1, I would highly advise doing so in a brand new sandbox org first to see if you got the same issues i’m seeing. 

For lack of a better explanation, the update broke our test org pretty much universally. Page includes not loading, loading broken, lazy load set pages loading on pageload, etc. etc. Video does a better job showing what’s going on. To confirm this was update related, last week we ran every page & function with our admins with no issues, at least not at the level we’re seeing post-update thank god for sandbox. Not shown in video is the pages showing the same type of erratic behavior in page preview.