I’m running the same version of WP and BP on both servers; field IDs are the same. I cannot replicate the issue on the testing server; I’m presently thinking it might be a PHP version issue.
I thought at one point it might be related to https://trac.buddypress.org/ticket/2171, but moving the custom profile field code to after the functions mentioned doesn’t do anything either…
Something else I forgot to mention — the “add friend” button now appears twice. Also, I don’t think it’s an issue with my theme — I tried switching to the BP default theme and adding a profile field during the members-loop and had the same issue.