tahtackle

Alright, solved it.

You can get the current post(id) by calling

$submission = WPCF7_Submission::get_instance();
$post_id = (int) $submission->get_meta( 'container_post_id' );

Sorry for spamming your support forum, but hey, self-solving problems amirite!
If my solution is kinda wonky or hacky let me know if there is a better way to do this.

Best,
Fabian

Okay, so I’ve figured out the error is because the filter has no access to the current $post. Trying to figure out how to access that. Pretty sure it’s possible since there are special tags for ID, URL etc, just need to find out how to get them into the filter.