Classically GTR predicts a slowing of time approaching the event horizon and that slowing is infinite at the event horizon. This is predicted to produce an observed red shifting of the signal and an apparent slowing of any object approaching the event horizon. With two black holes these effects should be magnified.
But the actual observed results are the opposite to those predicted by GTR, What is observed is increased frequency of the gravitation waves and increased speed.Equally black hole mergers occur in real time in a very short time of milliseconds. This proves the presence of infinite time dilation predicted by GTR wrong.