According to your description, I have the following questions to confirm with you：
- Does the web client have the same problem?
- Does the issue happen to all meetings and appointments?
- Have the users received the updated invitation in their mailbox?
I tried a series of tests and couldn't reproduce the issue. If you send an update out, the recipients will receive an updated meeting invitation in their Outlook. And the time stamp will be
modified as the picture below.
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