Niantic did not elaborate on the issue itself, which likely affected the ability to trade unlimited Lucky Pokémon, but has temporarily raised the game’s trading cap to compensate for lost time. ORIGINAL STORY 20/1/21: Pokémon Go has disabled the ability for all players to trade creatures with one another, following the discovery of a major bug last night. Around 11pm UK time yesterday evening, a user on top Pokémon Go reddit The Silph Road reported having traded 100 Pokémon with a friend, with all of them turning into Lucky Pokémon. (Lucky Pokémon have a higher base stats tier and are easier to power up, and are coveted among hardcore players.) An hour later, Pokémon Go developer Niantic announced it had pulled the game’s trading system worldwide while it “investigated an issue”. It’s now 12 hours later, and no further updates have been issued since. The issue here appears to be that the player traded Pokémon with a Lucky Friend - a temporary status two players can achieve through regular in-game interactions which guarantees the next Pokémon those players trade will be Lucky. However, rather than the status disappearing after the first trade was completed, the two players retained their Lucky status - meaning further trades also resulted in guaranteed Lucky creatures. More than 100 of them, in fact:

For now, players are waiting for further updates - though there’s a few comments from some fans once again surprised by the speed Niantic can act when a bug that is favourable to players is found.