It’s related to files I use in general (not necessarily used on the device that gets loop).
And it’s the same file in the sense of the loop (so if I restart Obsidian it’s the same in the loop as before restart). But not the same files every time I fix the loop by disconnecting and reconnecting, the next time it could be totally different files.
And once it also did the loop with an Obsidian file as mentioned in this comment Obsidian Sync stuck in syncing loop (re-uploading the same files) - #12 by nicolas.lienart