I noticed that when you restore an Android backup, the Trakt app doesn’t save your login info, so you have to log in again. It might seem like a small issue, but it’s a bit annoying.
It would be great if the app could be updated to store the login token securely when you get a new phone and restore your backup. Here’s a link with more info on how to do that: 사용자 인증 정보 복원 | Identity | Android Developers