Hi @arcanepsyche
Could you please share the JSON or XML export of the field group, the code to create the multi-steps form and the hook code that isn’t working?
Looking at @apmeyer’s code, I believe it will produce an infinite loop in the saving process. To avoid it, please take a look at this page: https://codex.wordpress.org/Plugin_API/Action_Reference/save_post#Avoiding_infinite_loops.
Thanks!