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Reason given: Is there a fix?
Walking lag glitch, previously known erroneously as Zero Error due to error codes that may appear during the text box matching method, is a minor glitch in Pokémon Red, Blue and Yellow. Exploiting this glitch causes lag before the player can take their next step. Sound effects may also be played with the lag or the game may freeze, depending on the player's coordinates.
There is no documented fix for the glitch except arbitrary code execution.
The glitch causes the route to become glitchy, and it will remain like that even when the player leaves the route and save and resets the game.
If the player loses, a text box may appear before the player is sent back to their black out location.
The glitch can be pulled off by two variations of the Trainer-Fly glitch. The first one involves changing boxes. The second one involves forcing an encounter with an unbeaten Trainer on the original route through 'text box matching'. Text box matching basically forces the game to load the equivalent text box for the last text box in memory, and is part of how the Trainer-Fly glitch works.
Example procedure (box change method)
1. Perform the 'fly away' part of the Trainer-Fly glitch.
2. Change boxes and reset the game.
3. Return to the original route where the player flew away and defeat any Trainer.
Example procedure (text box matching method)
1. Go to Vermillion City.
2. Walk up to the route north of Vermilion.
3. From here, perform a Trainer-Fly glitch by flying away from the trainer in the upper left hand corner of the route.
4. Choose to fly back to Vermilion City.
5. Walk to the route that is east of Vermilion.
6. Fight any trainer here. It does not matter who the player fights, as long as the trainer walks at least one step towards the player.
7. After the trainer battle, the player should go back to Vermilion and talk to the lady wandering about outside (her text box ID is 01) - see the image below for the lady:
8. The player should then walk up to the route north of Vermilion one last time and the player will battle the Trainer with a level 20 Squirtle (if the Trainer was unbeaten). The walking delay glitch will begin afterwards.
Vermilion Forest variant
When using the Trainer-Fly glitch in Vermilion Forest with the trainer right before the exit, when one of the trainers is battled then rebattled, the walking lag glitch will also occur, without any sound effects and there will be less lag.