iRule Errors when upgrading to v14.1

I had a similar issue on 14.1. I've figured out what behaviour has changed and what can be done to work around this.

My virtual server has two iRules, the 1st iRule has some header cleansing logic using "HTTP::header replace" this iRule has higher priority, it runs first. My second irule had some logic that sometimes triggers a HTTP response, similar to what you have above. HTTP::redirect triggers a HTTP response so the issue is probably the same.

It appears that you can no longer modify HTTP request headers if you trigger a response at the F5. You need to rejig your code so that "HTTP::header replace" only occurs after any possible HTTP responses have been triggered (and these should be followed by a "return" to stop processing the request).