FIXED
It was the “good” old structure bug. It’s a structure that was modified. I refreshed all blueprints nodes so I thought it would be ok (for the “basic” reference bug) but NOPE, the structure file was apparently corrupted. I had to make a new one, delete the bad one from the file browser, then replace every variable using it with a new one based on the good structure I just created.
Loved it.
Could structures be fixed on day Epic ? Please ? 