RT-AX86U – AiProtection + QNAP HybridSync Mount Failures After Updating to 3004.388.10 (Resolved by Downgrade to 388.9)

[themilfalcon]

Hi all,


Posting this in case others run into the same issue, and to understand if there’s a known cause.


Router: RT-AX86U (Zaku II Edition)
Previous stable: 3004.388.9 (Merlin)
Updated to: 3004.388.10 (Merlin)
NAS Setup: Two QNAP units (latest QTS), syncing daily using Hybrid Backup Sync (mount-based file replication, not rsync push)

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Issue After Updating to 3004.388.10​

Immediately after upgrading to 3004.388.10, my scheduled QNAP → QNAP HybridSync jobs started failing intermittently:

• Remote NAS hostname resolved normally
• Mounts would either fail outright, or mount but stall partway through file operations
• Manual sync attempts from QNAP UI also failed

No network, DNS, or NAS configuration changes were made — the only change was the router firmware update.

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Additional Finding:​

Although the web UI showed AiProtection enabled, the Trend Micro DPI components were not running:

• DPI processes were absent in ps
• No intrusion/web filter logs were appearing
• Restarting the firewall or toggling AiProtection did not start DPI services

This suggests that DPI / firewall module load order or initialization may have been affected in 3004.388.10.


Since QNAP mount and file sync flows pass through the DPI chain, this could explain the mount instability and stalled sync transfers.
Tried a hard reset and also tried a reset by clearing the NVRAM. The problem did not go away.

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Resolution​

I downgraded back to 3004.388.9:

• AiProtection / DPI processes immediately resumed normal operation
• QNAP HybridSync mounts and transfers now run fully stable, as before

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Request to Community / Developers​

• Has anyone else seen AiProtection not actually running under 3004.388.10?
• Is there a known change to DPI, netfilter hooks, or service startup order in this release?
• If needed, I can capture logs before/after.

Posting this in case it helps others diagnosing similar symptoms.


Thanks to everyone contributing to Merlin — it has been rock solid for my environment outside of this one case.

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[ColinTaylor]

Can you clarify:

This is a backup (or sync) between two QNAP servers. Are these servers on the same LAN, or are they in different locations and you're doing this over the internet?

As this is a Merlin sub-forum can you briefly explain what underlying protocol this "HybridSync" uses. You said it isn't rsync.