Setting database reference to null in OnDestroy resolved the issue (so far).

@chkuang-g is this related to the strong reference thing you're working on?

@stewartmiles We are experiencing this issue with Firebase 6.6.0, Unity 2019.2.8f1. unnanego's workaround does not affect the issue. It seems like a regression of the issue supposedly fixed in 6.5.0, (Desktop): Fixed the freeze when playing in the editor for the more than once or when closing the editor, when keeping a static reference to either FirebaseAuth or FirebaseDatabase instances

@unnanego
Your issue should be fixed in 6.6.0. Two things may be related to the freeze

• 6.5.0 fixed the freeze when playing in the editor for the more than once or when closing the editor, when keeping a static reference to either FirebaseAuth or FirebaseDatabase instances
  https://firebase.google.com/support/release-notes/unity#version_650_-_september_10_2019
• 6.6.0 fixed a couple to issues with database when play in editor.
  https://firebase.google.com/support/release-notes/unity#version_660_-_september_25_2019
  Could you verify if 6.6.0 fixed your issue?

@kevinfoley
It is very easy for us to miss a comment in a closed issue. To help us to better support your issue, could you create a new issue, follow the template and offer some more detail in it? Ex. Are you having the same freeze issue when play for the second time after calling GetValueAsync()? Could you find anything abnormal in your Editor.log?

Thanks
Shawn