Getting consumer pending messages count is inconsistent

[MENNAELMESALMY]

Observed behavior

I have a Jetstream that we add and delete messages from, on startup we want to get the count of messages in the stream as follows:

var currentCount = sub.GetConsumerInformation().CalculatedPending;

We noticed that this sometimes returns a count more than the actual messages in the stream so for example, we see it returning 1882 while the stream only contains 1867 messages, we checked the count with nats stream info <stream-name> and it had indeed only 1867.
Also, we check for the last message with msg.MetaData.NumPending == 0 but we observed it having it set to 15 when in indeed it was the last message on the stream as per the cli nats sub <subject-name> --last-per-subject.
Setting the ackpolicy to .WithAckPolicy(AckPolicy.None) makes it return the correct count for some reason.

Expected behavior

The returned pending messages count is consistent with the message count in the stream.

Server and client version

Server version: 2.9.16
Client version (c# client): 1.0.4

Host environment

No response

Steps to reproduce

No response

[ripienaar]

You are running a very old server and there have been 100s of bug fixes since.

Please let us know if this is still happening after you upgrade to latest.

[MENNAELMESALMY]

will do, Thanks!
do you know of any particular fixed bug that can result in this behavior?

[ripienaar]

You can look through the changelog to see, it's not worth diagnosing bugs on such old versions at this point and so I wouldn't be certain which of the many fixes would impact you.

So to help us help you, please upgrade.