Thanks, John!
This was similar to how I solved it yesterday 🙂
I got it almost working, but I need this on 5 relationship fields on the page.
I’ve tried to add the filter 1 time for each realtionship field, but then it seems like not all of them are run.
Maybe 5 are too many.
I tried this:
add_filter('acf/update_value/name= ...
add_filter('acf/update_value/name= ...
add_filter('acf/update_value/name= ...
add_filter('acf/update_value/name= ...
add_filter('acf/update_value/name= ...