I can now manage this issue to my satisfaction, so I haven’t gone through all of the steps. Just sharing as it may be useful to developers and other users.
Steps to reproduce
Run Obsidian Sync on an Android device with low free space (e.g. 2 GB or less).
At some point, when I open the Obsidian app on Android, I see the “reindexing vault” notice and I see that the sync icon has been replaced by the “no syncing” icon.
Check settings: The vault is no longer synced at all – looking at sync settings, it’s as if the device was never synced. I wait for reindexing, restart obsidian, then restart land of ice, but nothing helps.
Reconnect sync on the Android device. All good.
Then at some point it happens again – the next day or weeks later. And the whole process repeats.
When this was happening a lot, I asked ChatGPT for ideas. One of the many suggestions was to ensure adequate free space. I have a bad habit of running my devices with too little free space, so I tried making more space. It seemed to work.
The problem disappeared for months. I have been observing this on two devices, and it seems consistent. I was keeping the devices’ free memory high (it was 5 GB or more for several months on one device, then the other). The disconnection has never occurred.
Reoccurrence:
Yesterday I downloaded a bunch of stuff on my Android all at once and I was down to around 1.7GB free space at one point. Then today I opened Obsidian and I see the “reindexing vault” notice and the “no syncing” icon.
So I’ve again cleared space and reconnected the vault.
Related posts: similar issues have been shared without resolution, but I can’t remember how to properly link them to this post (unless I post the raw links here).