I’m having the exact same issue here.
It’s important to note the in the case, People Profiel (NL) is the Post Type where he’s trying to add a relation (Project (NL) ) to.
In my case I have two CPT, Products and Solutions which I’m trying to add a relation from a Library CPT.
In either case, when I add the item, both sides show “Library” as CPT, as expected, but when I save it becomes the name of the post I’m into, “Products” or “Solutions”
Any clue on why it’s happening?
Thanks!