Continuity mistake: When Alex goes home in the night, he turns on his cassette player, takes out a cassette from the player, then after a few seconds a closeup is shown of the slot with a cassette inside that he removes again. (00:18:25)
Continuity mistake: When Frank first pours the wine for Alex he fills it all the way to the top. The shot changes and he is still pouring the wine however the level of the glass has dropped to half full and he fills it up again.
Continuity mistake: When Alex is informed that he's being transferred to the Ludovico center, the governor's arms jump from his lap to under his chin, then back to his lap. (01:06:00)
Chosen answer: The droogs didn't like how Alex was leading them, so he attacked them. It's never explained whether the plan was to set him up all along, but given that Din was ready with the bottle to smash him over the head, it seems like an opportunity to be rid of him came up and they took it.
Captain Defenestrator