Complex sentence: Another possible reasons for failure was inadequate preheating of catalyses beds for the pulsing rocket thrusters: hydrazine fuel decomposes on the beds to make hot gasses that throttle out the rocket nozzles, cold catalyses beds caused misfiring and instability in crash review tests.
Split into simpler sentences: Another possible reasons for failure was inadequate preheating of catalysis beds for the pulsing rocket thrusters. Hydrazine fuel decomposes on the beds to make hot gases that throttle out the rocket nozzles; cold catalysis beds caused misfiring and instability in crash review tests.