I am afraid that this issue cannot be analyzed based upon the provided information. You may please arrange the PST file with even this single message only, to re-produce the issue. Until and unless this issue is not re-produced here, we may not be able to provide assistance.
We are sorry for the inconvenience caused to you in this regard.
Could you please share your sample PST file with us for our investigation? If it works with version 5.5.0 and fails with 6.9.0, then we need to report it as regression to our Product team. Also, please try the latest version of the API i.e. Aspose.Email for Java 16.11.0 and see if it resolves your problem. Otherwise, please share your sample PST file with us for further investigation at our end.