After upgrading to 10.8.3 it appears the back office is broken for all non admin users
I am referencing this GitHub issue that I am experiencing a similar out come, where did this land?
https://github.com/umbraco/Umbraco-CMS/issues/15435
If upgrading to the next major is the solve, ill have to speak internally to solve this as thats not a true desireable option at the moment...