That makes complete sense. If you listen to that passage very loudly with headphones on (I have noise cancelling ones), that's what it sounds as though happened. You hear a 'thud' or a 'bang', as though somebody fell over. Then you hear one or two, very concerned voices. It's incredible that the performance simply continued along.
I've always dismissed allegations that the BPO trombones didn't play there because they simply didn't like Bernstein. That explanation never made any sense to me. You can hear quite clearly that SOMETHING happened at that spot.