Problem:
The issue here is that the user has their child form which gets some basic parent information from the URL. However after submitting the form and then being redirect to the same child form to add a new child post for the same parent the link to allow the user to click to the parent is broken again.
Solution:
The workaround to this is by using the [wpv-post-url] in combination with the [wpv-search-term] shortcode.
The way to get the url from the Parent id in the url can be seen below.
<a href="[wpv-post-url item='[wpv-search-term param='parent_planner-event_id']']">Back to [wpv-post-title item='[wpv-search-term param='parent_planner-event_id']']</a>
Where parent_planner-event_id is the url parameter.