I would open a support ticket with Zimbra straightaway.
FWIW we use HSM and have not any issues like this. Since I keep pretty much all of my emails (even from before using Zimbra starting a few years ago!), my mailbox is one of our biggest utilizers of HSM and I have never seen this issue on our farm nor on any of our clients' systems.
All the best,
Mark
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___________________________________ L. Mark Stone, CIO "Uptime. All the time."
477 Congress Street | Portland, ME 04101-3431 | (207) 772-5678
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