I have not seen this before, but it may have occurred without being captured so dramatically on video.
Frame 15 shows the mechanism as it should be; frame 16, half a second later, shows all hell breaking loose. 4 coincident mates and 2 hinge mates have let go, and 3 bodies are tumbling through space.
In between the two frames, the integration halted, but the timeline clock kept ticking, the video kept rolling although the image was frozen, and the frames were rendered by PW. No messages were displayed and the logs give me no clue.
This is not supposed to happen.
Does it ring any bells for you?