There are always heaped messages in some partitions as displayed on the monitoring page.
The producer keeps producing messages to the partition while the consumer never consumes these messages
You can restart the client if messages in some partitions are not consumed. If the problem persists, you can either check the client logs first or submit a ticket for assistance.
There are insufficient consumers in the consumer group or the consumption speed is too slow
Try increasing the number of consumers to improve consumption speed.
The consumer does not consume messages in certain partitions due to bugs
Check the local logs of the consumer to see whether exceptions exist.