I don't speedrun contra, but I watched Summoning Salt's video on Contra and heard about the random hardware error glitch. Today I watched a Veritasium video called The Universe is Hostile to Computers and it might have an explanation as to why that happened. It talks about radioactive particles and their effect on computer chips. It caused 1s to switch to 0s. It might not be why though, so let me know if I'm wrong.
I think this is called a bit flip or something and it happens rarely, but depends on where you are on earth or in the universe. it can also be due to the cardrige not properly inserted, I remember they found a glitch like that for mario 64. It sounds like trying to manipulate the real life RNG ahah