When receiving this error, it can also be observed from the Audit logs that there are at least 2 entries of the same Digest Inline Action.

This can be encountered when a URL Click Tracking service is enabled on the mail client. In most cases, it is observed on Outlook due to Microsoft's Safe Links.

URL Click Trackers provides URL scanning at the time of click. The scan action can trigger the Digest Inline Action before it redirects to the actual result. This causes duplicate quarantine release requests, thus prompting the error.

To prevent this, it is suggested to disable URL click tracking for Emails coming from Trend Micro Email Security. You can instead enable a similar functionality on Trend Micro Email Security, which is the Time-of-Click.