HI @gjgerv, thanks for reaching out.
The “Cannot modify header information – headers already sent by” error message typically indicates that something in your PHP code has caused output to be sent before the HTTP headers are fully defined. It’s been linked to another plugin loading WordPress core files out of order in the past, which is a possibility here.
To rule out plugin/theme conflict try to run Wordfence as your only enabled plugin and also reverting to a default theme such as Twenty Twenty-Three. If you no longer see the error, reenable your plugins and theme one-by-one until it recurs again to help find the cause.
If the above step fails, Please delete the Wordfence plugin directory located below:
~/wp-content/plugins/wordfence
The steps to follow when removing wordfence are documented here: https://www.wordfence.com/help/advanced/remove-or-reset/#remove-or-reset
Now install Wordfence on the WordPress Plugins page, and check whether you still see the PHP warnings.
Let me know if this helps.
Thanks,
Mark