Editor is freezing after updating Unity from 2018.3.14 to 2018.4.X

Hi,

we recently updated Unity from 2018.3.14 to 2018.4.1. We experiencing that the Editor is freezing after the second time leaving the "Play" mode. Entering the "Play" mode for the first and second time always works. The Editor seems to be "stable" and without unexpected issues before leaving the "Play" mode for the second time. After leaving the "Play" mode for the second time the Editor is freezing on any action. Even closing the editor will end up in a freeze. The Editor process in the Task manager is "Not Responding" and has 0% CPU load.
We have to kill the process with the Task Manager and to restart the Editor.

Our attempt to reimport all assets failed to fix the issue.
We deleted all following folders too but with out any impact on the issue:
[ProjectPath]/Library
[ProjectPath]/obj
[ProjectPath]/Temp
[UserPath]/AppData/Local/Unity
[UserPath]/AppData/LocalLow/Unity
[UserPath]/AppData/LocalLow/[CompanyName]
[UserPath]/AppData/Roaming/Unity

 

We have been able to fix it.
Removing the Debug flag from the Firebase plugin fixed the issue.

 

hello,
would you elaborate more on "removing the debug flag" and where this is done because we're having the very same problem and it is November 2019