For the URL, I’d like to be able to reproduce the problem, in an environment where I can look at the log files myself.
So if I get the 406 Not Acceptable error on the UR:
The bit I’m interested in is the bit after the mydomain.com, and a description of what you did to get the error.
As an aside, you could also benefit from learning to manage/modify your standard mod_security OWASP application firewall rules:
is the basic set, and:
https://www.feistyduck.com/library/modsecurity-handbook-free/online/ch01-introduction.html
is a really useful online resource for learning about and dealing with this type of issue.