Hey Karen,
If you do this more than once, do you consistently see the 500 Internal Server Error? It looks like (in this example at least) PressForward is requesting admin-ajax.php and missing it for reasons unknown.
I’ve seen this happen before when databases get too heavy and the page times out, but that seems unlikely in this case (816ms is less then a minute before the page is returned).
A look at your servers error logs after immediately inducing the error might be useful, but I’m not sure what could cause it other than a timeout for one AJAX function but not the other (the Relate action seems to go off without a hitch). Potentially it could be a bug in our nomination code, but it is very odd that it wouldn’t happen with anyone else. I can verify that the nomination process works well elsewhere.
There is a possibility here as well, a problematic function that executes before the Nomination process but after the Relate process on the AJAX page, one that isn’t part of PressForward, an external plugin or theme element that could be causing the issue.
Is it possible to, either in your site or a staging version of the site with all the pieces in place, turn on WP_DEBUG and see if the response from the nomination no longer 500s and instead returns some sort of failure information?
-Aram