[Bug] Backlog abnormal increase in a delay queue

### Search before asking

- [X] I searched in the [issues](https://github.com/apache/pulsar/issues) and found nothing similar.

### Version

OS: tlinux(CentOS)
pulsar-broker-version: pulsar-2.10.0

### Minimal reproduce step

This is a persistent partitioned topic, acctually we made it a delay queue, means that we do not consume msgs and send an ack immediately.
After a period of normal operation，some of these partitiones became unhealth. We found those partition's backlog was increasing abnormal, but there wasn't any logs helpful.
We tried to clear-backlog for the target subscription of the abnormal partition, the backlog decrease rapidly, but soon became abnormal again, as the following pic.

### What did you expect to see?

All partitiones of these topic became nromal.

### What did you see instead?

As I described in "Minimal reproduce step"

### Anything else?

_No response_

### Are you willing to submit a PR?

- [ ] I'm willing to submit a PR!