Pokemon Go might have gotten rid of the "three step" bug, but players are learning about a new glitch that can make catching Pokemon frustrating. Players are reporting that after catching a wild Pokemon, it will become a totally different Pokemon after it's placed into their box. So, a player might think they've caught a Golduck in the wild, but that Pokemon will actually be a Pidgey (with identical stats) when they next check their collection.
At first glance, many trainers thought they caught a Ditto, an elusive Pokemon that can transform into any Pokemon it sees and has not yet appeared in Pokemon Go. However, upon further examination, most fans agree that this is a new bug introduced in the game's most recent update. The bug seems to affect both iOS and Android users and there's no known explanation for how and when it occurs. It's also possible this bug is somehow related to the Legendary Pokemon that allegedly appeared at gyms last night.
The "transform bug" might be frustrating to players who thought they had caught a new Pokemon only to discover that it's actually a Pidgey or Weedle, but it does have one slight upside. You'll still receive the 500 XP for catching a "new" Pokemon, even if it turns out to be a Rattata in disguise.