Background: A couple of years ago, I added two Access Restriction rules to limit access to the Admin panel. They both seem to work. I cannot access the panel when I deactivate them. One rule contains my local IP range (i.e. 172.16.0.1 - 172.16.0.255). The other rule contains the single public IP address of my proxy.
I can access all of my Admin panel via local IP address and from my proxy IP address.
The problem that I encounter is that I get a generic 403 or a "Error Oops, something went wrong (Forbidden). Please try again." error message when I try to edit certain things in the Admin panel via the proxy. I can edit anything via local IP without issue.
So far, I have found that I get the permission error when trying to activate/deactivate any block in Design->Layouts and when trying to create or save edits to a product. I can save edits under Setting->General. Again, this issue only affects access via the public proxy.
This is all that I have tested so far.