Max Raid Battle item glitch

From Glitch City Wiki

The Max Raid Battle glitch item glitch was a glitch on June 30, 2020 (patched shortly afterwards on the same day) in Raid Dens in Pokémon Sword and Shield. It caused the player to seemingly obtain nameless glitch items after the battle, thus causing the game to close from an error message.

Screenshot of the glitch

YouTube video by PokeTips