Experimental test of local observer independence. M. Proietti, A. Pickston, F. Graffitti, P. Barrow, D. Kundys, C. Branciard, M. Ringbauer and A. Fedrizzi in Science Advances 5: (2019).  What the paper says?

Wigner's friend

The question whether the observers’ narratives can be reconciled has only recently been made accessible to empirical investigation, through recent no-go theorems that construct an extended Wigner’s friend scenario with four observers