Hi @aussymac ,
It seems the error size is larger then the set limit.
You can try to increase the header size from Apache using
<VirtualHost *:80>
ServerName site.com
# Increasing the HTTP Request Header Size
LimitRequestFieldSize 16384
Also the configuration needs to be increased in publish AEM instance configMgr for "Header Buffer Size" property in "Apache Felix Jetty Based Http Service”.
Hope it helps!
-Tarun