Loses frame theme when using "Return to previous page" -link after error message

I tried to use script
https://demo.virtualmin.com:10000/virtual-server/all_webmin.cgi
to update virtual servers when using normal domain user account. That was prevented which is good. But when trying to use "Return to previous page" -link the frame theme broke. The left frame bar dissapered totally and navigation became impossible.

Status: 
Closed (fixed)