Adding/editing a task
(1) When adding a task from the widget the labels drop-down box is often disabled. I've not identified a particular circumstance when this happens. It seems sporadic. After adding the task I'm always able to assign labels to it from within the Todoist app.
(2) When editing a task in the Todoist app the back button dismisses any changes whereas a check mark button on the top control bar saves any changes. I'm not a dev but I think that this actually violates Android design guidelines. The back button should always save any changes while a button with an X mark should be shown for canceling any changes.