Time Machine backup to Synology NAS keeps hanging — eventually triggers watchdog panic on reboot (macOS Tahoe 26.0.1)

TL;DR: On macOS 26.0.1 (Tahoe), Time Machine over SMB to a Synology NAS hangs almost daily during “preparing backup” or “cleaning up.” The backup drive disappears from settings, and on reboot, macOS throws a watchdog timeout kernel panic referencing smbfs. Only a full NAS + Mac restart temporarily fixes it.

Hey everyone,

I’ve been running Time Machine through a Synology NAS (DSM 7.2.2) using SMB, and I’m running into an issue that keeps happening almost daily.

Time Machine will function properly for most the day, but then without rhyme or reason, it will start normally, and then either hang on “Preparing backup” or during “Cleaning up” after it finishes. When that happens, the backup target disappears completely from System Settings, as if I never set it up — but the sparsebundle still exists and is accessible through Finder on the network share.

Once it gets into this state, I can’t reconnect Time Machine to the NAS unless I restart both the NAS and my MacBook Pro. Unfortunately, when I restart the Mac, it hangs for a couple of minutes, then throws a watchdog timeout kernel panic before booting back up.

My setup: Apple M3 Max 36GB 16-inch MacBook Pro

NAS setup: Synology DS418 running DSM 7.2.2 - 72806 update 4

Error Details (header)

panic(cpu 0 caller 0xfffffe0046b7475c): watchdog timeout: no checkins from watchdogd in 182 seconds (7933 totalcheckins since monitoring last enabled), shutdown in progress, vfs shutdown not yet started
Debugger message: panic
Memory ID: 0xff
OS release type: User
OS version: 25A362
Kernel version: Darwin Kernel Version 25.0.0: Wed Sep 17 21:38:50 PDT 2025; root:xnu-12377.1.9~141/RELEASE_ARM64_T6031
Fileset Kernelcache UUID: 20CF9810092CBB5E33B6F0FEE89AF7EC
Kernel UUID: F2BBDEDB-5775-3524-A4FC-6317AD50CC37
Boot session UUID: 14A370D9-1390-4887-8A55-F0DD1BA9F7BB
iBoot version: iBoot-13822.1.2
iBoot Stage 2 version: iBoot-13822.1.2
secure boot?: YES
roots installed: 0
Paniclog version: 15
Debug Header address: 0xfffffe00248e9000
Debug Header entry count: 3
TXM load address: 0xfffffe0034850000
TXM UUID: B3AB0C13-2C56-3E49-8B2A-382CE92C9F9D
Debug Header kernelcache load address: 0xfffffe0044850000
Debug Header kernelcache UUID: 20CF9810-092C-BB5E-33B6-F0FEE89AF7EC
SPTM load address: 0xfffffe0024850000
SPTM UUID: F5976B2D-35A1-368B-BA9B-A1908E2A91C0
KernelCache slide: 0x000000003d84c000
KernelCache base:  0xfffffe0044850000
Kernel slide:      0x000000003d854000
Kernel text base:  0xfffffe0044858000
Kernel text exec slide: 0x000000003f018000
Kernel text exec base:  0xfffffe004601c000
mach_absolute_time: 0x1bc6e920b30
Epoch Time:        sec       usec
  Boot    : 0x6900f4b5 0x00020d1d
  Sleep   : 0x00000000 0x00000000
  Wake    : 0x00000000 0x00000000
  Calendar: 0x69022b59 0x00060dd5
...