Pokémon Go: Error 29 is a mystery in itself. This error has been in the game for quite some time now with no certain solution. The developers are in a dilemma as they haven’t been able to get rid of it even after multiple update patches.
Root Cause ?
Pokémon Go: Error 29 pops up if the user tries to re-join a gym battle after abandoning it midway. When the user leaves a game or quits midway, the game doesn’t update its database or say doesn’t register that the user left the battle. So, for the next 10-15 mins this error pops up on the user’s screen every time he attempts to battle in the same gym.
There is no way to fix this from the user end other than waiting out the remaining time period. As of the developers, they are still trying to figure out!
We got a few solutions for the users as of now.
Solution 1: Don’t quit !
Players often leave the gym after defeating the 1st Pokemon to replenish their Pokemon. So the obvious solution is, don’t quit and continue challenging the 2nd Pokemon. This way, even if the player loses, they can replenish their Pokemon and battle at that gym again instead of getting locked out of it.
Solution 2: Move on
The bug won’t show up if the player tries to battle at another gym. This resets the values in the back-end of the game after the 1st round, hence the player can go back to the old gym and resume the match without receiving any errors.
Solution 3: Wait
The only solution considering the worst case scenario, like if there are no other gyms nearby to go battle or the player doesn’t have enough potions to replenish their Pokemon. The wait period is mostly 15 mins, sometimes it may be a bit more, as after that time the values are reset in the game’s back-end.