Created attachment 36851 [details] Accurate example configuration snipped > Environment Binaries are installed on a CentOS 7 (rel. 1905 - x86_64) on a EC2 vm (official hvm AMI) via stock yum repositories (no third party repos are configured, except from MariaDB 10.2 repo for clients). > Alerts Service is apparently running without any issue. Logging is set in VirtualHost context and includes INFO level. > Configuration details For your discretion, i must advice you that configuration is built through extensive use of mod_macro from virtualhost context and above, but i'm quite sure it's not involved. Indeed, misbehaving directives are all configured by the same macro, which is called once for each VirtualHost (example snippet is "macro expanded") and resulting configuration is triggered correctly. > Unexpected Behavior Despite several trials of "Header edit", pattern is never rewritten. It looks like Header edit is not able to match commas (added by Header merge directives). I suspect its input has been split upon separating commas by a preceding parser or it's fed by an outdated or null header referral.