Hello @Mad3 

As per your statement is all Client script/Ui Policies not working or specific one not working? If specific, try to add some alert statement over them and see if anything showing up.
The instance which are upgraded on Xanadu version, is it same?
As suggested by Atul do perform cache.do 
Try to check from another browser? Also, see if the Client Script/Ui Policies are applicable to persona user you testing?
If still no success, then last option log HI Case where an engineer can help out. 


If my response has helped you hit helpful button and if your concern is solved do mark my response as correct.
Thanks & Regards
Viraj Hudlikar.