I encountered this bug while playing A CO-OP vs. AI match versus intermidiate bots while playing Blitzcrank. The problem was, when I tried to pull one of the bots to me, halfway they would stop, the animation would be kind of frozen, then disappear and they would go on and behave normally after that. This happened three times, it didn't happen every time.
How to recreate this bug:
1. Start a Co-op vs. AI match against intermidiate bots.
2. Pick Blitzcrank
3. Use your Q to pull try and pull the bots on the enemy team
I think it will probably occur at about 40% of the pulls, only on champions. As far as I know, it occurs for sure when pulling alistar.