Why does my ability/rating against bots vary? I've recently started playing chess again and am training against the chess.com bots.
I've been able to blaze through the lower rated bots and started to get stuck around the 1100s with having to take time with my games to get past them and recently beat a 1500 bot.
However, I've found an old page open with a 550 bot (Oliver) and, although rushing the openings, I haven't been able to consistently beat him.
Is this variance in being able to beat 1500, but still have challenge with much lower ratings normal?
The bots do have a lot of variance, especially the weaker ones. I just tried playing Oliver and he hung his queen on move 3. If that happens you're obviously going to have an easy game.

and started to get stuck around the 1100s with having to take time with my games to get past them


although rushing the openings, I haven't been able to consistently beat him.

So when you play the stronger bots, you take your time, and when you play the weaker ones, you don't? That explains it. It's pretty easy to get into a losing position fast if you aren't taking the game seriously enough, even against a weak opponent. This can happen both against computers and against real players.