If the task was once checked as done and then unchecked again, it goes back to the list, but all notes are lost. I can see them from PC, but android phones shows the task, but notes are empty.
Which version of the Android app are you running? Please make sure it's updated to the latest version, 3.0.7.
Was the note created originally on the mobile version or the web version?
Using the latest version of the app.
It was created on PC.
I have now been able to reproduce this issue, I have let the devs know about it.
This will be fixed on 3.0.9. It will require logging out and back in again once updated.