Absolutely YES: we are not talking of the same scenario. My scenario is the following (perfectly symmetric): 2 spaceships, four mirrors, two detectors (one for each spaceship and observer) M and M' are sitting in the middle of two transparent spaceships. The two spaceships are equal and are moving one towards the other. There are two mirrors inside, one in front and the other back, equidistant from M in M's spaceship and equidistant from M' in his spaceship. M keeps his own detector as M' holds his detector in his hands. Both detectors point to both mirrors, emitting a signal (a sound or chime and a led lamp blinks) from the light received from each mirror. You can imagine to observe the scene from the pov of a third observer M° who is constantly midway between M and M' When the the two spaceships are getting so close to slide one onto the other, M and M' put a flint out of window and the scratch of the two flints will provoke a spark exactly were M° is sitting. Obviously, M° sees and listens at the two chimes simultaneously, because he sits where the two spaceships meet. The spark event occurs in the point where the spacetime lines of M and M' cross each other. Same x position but slightly different z position (level). M, M' and M° have the same right to consider the spark event as belonging to their reference system, as if they were motionless respect to the spark. Then they hear a simultaneous double chime and see two simultaneous LED light blinks in their own detector. After some nanosecond they will also see the image of the other's detector faraway corresponding to a double simultanous blink. Don't try to solve the paradox saying that the spark event "belongs" only to M°. Also M and M' consider their own image of the spark as belonging to their system. This is the reason why their detectors will receive the signals from both mirrors simultaneously. the paradox exists ony if you consider light as a single thing propagating.