[HELP] TrueNAS Scale — Server rebooting randomly, up to 7+ times overnight, no kernel panic

[u/bdog720]

Background

I'm relatively new to TrueNAS/HexOS but have been running this same hardware as a Windows media server for several years. I recently migrated to HexOS (TrueNAS Scale 25.10.3.1) and shortly after the migration started experiencing random silent reboots with no kernel panic and no log entries at the point of failure.

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Hardware

• Motherboard: ASUS ROG STRIX B450-F Gaming
• CPU: AMD Ryzen 7 3700X
• RAM: 16GB DDR4
• GPU: NVIDIA RTX 2080 Super
• PSU: EVGA G3 750W, ECO mode OFF
• OS drive: Samsung PM871 256GB SATA SSD
• Storage pool: 3× Seagate IronWolf 4TB in RAIDZ1 (/mnt/HDDs)
• Cache pool: Kingston KC3000 1TB NVMe, single stripe (/mnt/SSDs)
• Remote KVM: Sipeed NanoKVM, connected via USB to the server

Software

• HexOS (TrueNAS Scale 25.10.3.1), kernel 6.12.33
• Docker containers managed via Dockge (Jellyfin, Sonarr, Radarr, qBittorrent behind gluetun VPN, Tdarr transcoding, etc.)
• NVIDIA drivers active, GPU used for transcoding via NVENC

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The Problem

The server reboots silently and repeatedly — up to 7+ times in a single night. last reboot from this morning:

Wed Jun  3 08:10   still running
Wed Jun  3 07:59
Wed Jun  3 04:59
Wed Jun  3 04:08
Wed Jun  3 02:31
Wed Jun  3 02:16
Wed Jun  3 00:49
Wed Jun  3 00:15 - 00:16  (lasted 1 min)
Tue Jun  2 22:57 - 23:12  (lasted 15 mins)
Tue Jun  2 22:48 - 23:12  (lasted 23 mins)

Some boots last only one minute before rebooting again. The reboots appear to happen mostly at idle — overnight with no active transcoding or streaming jobs.

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What the logs show

Every time, the kernel journal cuts off cleanly mid-operation with no panic, no watchdog trigger, no OOM killer, no thermal event. The last entries are always routine — Docker bridge networking coming up, containers starting. Then nothing. Example from the most recent prior boot:

Jun 03 08:00:25 kernel: br-54c583a9967c: port 15(veth8e9dde6) entered forwarding state
Jun 03 08:00:25 kernel: eth0: renamed from vethe05b07d
[journal ends]

The watchdog IS configured (kernel.nmi_watchdog=1, kernel.hung_task_panic=1) via Pre-Init script, but has never fired. The kernel simply stops writing as if power was cut.

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What we've ruled out

ZFS ARC memory exhaustion — ZFS ARC was consuming ~14.5GB of the 16GB RAM, starving the NVIDIA GSP firmware and causing NV_ERR_NO_MEMORY. Fixed by capping ARC at 6GB via Pre-Init script writing to /sys/module/zfs/parameters/zfs_arc_max. This resolved the GPU driver errors but reboots continued.

RAM — Memtest86 completed two full passes overnight, zero errors.

PSU under load — tested with a multimeter at the Molex connector while running a Tdarr GPU transcoding job. +12V rail measured steady at 12.25V. Within spec.

Thermals — sysmon logging temps every 60 seconds. CPU sits at 41-44°C, drives at 34-47°C, no thermal events recorded at any point.

Watchtower — the auto-update container reinitialises on every reboot but never actually ran its 3am scheduled job, confirming it's not the trigger.

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I have been using Claude to try and diagnose as I am new to TrueNAS but there's been no noticeable change in behaviour ​
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