Version information and more: https://pastebin.com/Y6vYSuqT
How to replicate:
Go to classroom.google.com
Select pending assigment
Add or create -> File
Get following pop-up: https://i.imgur.com/aKLdc19.jpg
After that pops-up, you can't interact with the page in any way. Some animations still work, but you're pretty much forced to reload.
It's pretty weird, because adding an exception for classroom.google.com doesn't seem to fix the issue (nor, enabling Filter-HTML). However, the website works nicely when I completely disable LocalCDN.
On DevConsole->Network, there's no difference beetwen loading the page with LocalCDN On/Off
Without LocalCDN the browser console throws no (relevant) error.
With LocalCDN enabled, the following error pops up 4 times (with varying "parameters"), before displaying an indefinite ammount of varying uncaught errors.
Cross-Origin Request Blocked: The Same Origin Policy disallows reading the remote resource at https://www.gstatic.com/_/picker/_/js/k=picker.opms.es.202bjJe2xTc.O/am=EA/d=0/ct=zgms/rs=AGshSGMw0BjnWi0H0j2rOfTQh-KFvBQt9Q/m=sy21,uiNkee,K99qY,Jdbz6e,Mq9n0c,uGhL7d,eSRHqc,O6y8ed,MtdDwc,HqHEue,PwNT6,X5SV6b,kb0Hd,sy6,OR2UYd,Qxnz7b,A0O7S. (Reason: CORS header ‘Access-Control-Allow-Origin’ missing).