Well, all it needed was a hit with a hammer a few times on the bolt head.
I always thought that reinforcement was meant for the upper hinge, but it's for the lower.
Upper hinge (seen from inside on the picture above) is held by two layers of aluminium and while the outer one, that we see, cracks, inner layer still holds ok.
Lower hinge has just one layer, but cracks are not visible while the hinge is in place.
I used Loctite 3455 to glue the reinforcement part in place and also secured it with one bolt, just in case.