Observations about sync stuck at 95%

May the following piece of info be of help to maintainers and users.

I have multiple devices running syncthing 1.23.7 and one still at 1.23.6. All these devices have been running well since a while.

There was one device that broke down at one point last year. Physically broken (RAM and CPU or something). I was not able to remove this device from my cluster and the index in a normal way, because I could not even start this device anymore, because of blue screens. This old device, let’s call it M, still shows up occasionally during sync problems.

The last few weeks, i was debugging a stuck at sync problem. I was successfully able to get rid of it and now all devices and all folders are “up to date”, so I cannot share screenshots.

The problem:

  1. some files were not synced across devices.
  2. When looking at those files under “external devices” section, the device M was shown as modifying or originating device, but none of my existing devices and folders are shared with M.
  3. Because of M showing there, i was not able to locate which device was not up to date or made trouble, because they ALL were stuck at syncing and they all showed M as the culprit.


The key point was to turn on all devices that were synced to a particular folder at once. Turns out, that all other devices somehow tried to sync a file, which originated from M to this one device, which had been turned off. Also, two of the other devices had not yet shared their folder with that device.

The “weirdness”.

All these devices had been up to date already with each other long after M was broken. The stuck in sync file originally was put by M into the common index, but meanwhile, all other devices should have had an up to date index and when a change to the files occured, not M should have shown to not be up to date, but the actual device, which was offline. At least that’s how I imagine it.

Is there a possibility to make this more clear in the UI?

Alternatively, is there a possibility to purge traces of this old device M from the index, while keeping the files intact?

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