An issue that might arise is the Android app losing the authentication Token for some reason and you not noticing immediately.
Once facing this issue, you will have some items not synced with the server and if you delete the accoun to re-add it, you will lose them.
On a selfhosted EteSync server you will get lines such as the following :
INFO: ::1:28393 - "POST /api/v1/collection/list_multi/?stoken=Y2TMWsPY5RXf4tUBDmAIXQpCgf8h9scN HTTP/1.0" 401 Unauthorized
INFO: ::1:51824 - "POST /api/v1/collection/list_multi/?stoken=Y2TMWsPY5RXf4tUBDmAIXQpCgf8h9scN HTTP/1.0" 401 Unauthorized
INFO: ::1:42106 - "POST /api/v1/collection/list_multi/?stoken=Y2TMWsPY5RXf4tUBDmAIXQpCgf8h9scN HTTP/1.0" 401 Unauthorized
One way to prevent this is to use the option in the Android app account's settings : Encryption password (change your encryption password)
, where you can reuse the same one as before). That gets you a new token and the items are not lost but will get synced with the server.
Solution taken from https://github.com/etesync/android/issues/227