Take it to nintendo. They repaired my N64 for $60 USD.
Afaik it means it had an error reading the cartridge. Happens to mine all the time. Give the cartridge the ol' seductive blow and it usually works.However if the NES connector is too corroded, it needs to be repaired or replaced.
Sometimes rubbing a Q-tip lightly with alcohol and then spreading it around the inner part of the cartridge helped meidk i though i think that has some bad effects though
its okay to use alcohol as long as it has a high alcohol concentration
Obviously you're having a run in with the Glitch-Gremlin.
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