This is a thought experiment. Consider two photons traveling at right angles and intersecting at some point. As seen from Earth these photons will not interact with each other because their energy is too low for particle creation. Now consider a rocket traveling at high relativistic speed towards the intersection point. People on that rocket will "see" these photons extremely blue shifted. They would appear as gamma rays. Now from the rocket point of view there is a higher probability that particle creation would occur, because these photons appear so energetic. Any produced particles like electrons or positrons would be captured by the rocket and brought back to Earth as a proof. The experiment could be repeated to get good statistics. How many particles would that rocket bring to the Earth. None? Or maybe the amount predicted by observers on the rocket?
Disclaimer. I am not a physicist. Probably this "paradox" has a very simple resolution just like other relativity paradoxes. I probably made some wrong assumptions.