Huge Kafka __consumer_offsets topic

I have a problem with the topic __consumer_offsets, the topic is very large, kafka metrics show that I have 4 billion messages on it, I suspect that message compaction does not work correctly, I constantly see an increase in new messages in the metrics on this topic (however, the total log dir size fluctuates periodically between 19 and 20 GB). What could be the reason that this topic is not being cleaned up?