It looks like after the toolbox is opened, any panel opened before the debbuger will be fine but any opened after will be blank/broken.
Bug 1706703 Comment 14 Edit History
Note: The actual edited comment in the bug view page will always show the original commenter’s name and original timestamp.
It looks like after the toolbox is opened, any panel opened before the debugger will be fine but any opened after will be blank/broken.