There is a way to reproduce the bug I found. And it is possible for Firefox to basically get into this state on its own, so it's possible that this is the reported problem. It should be reproducible by unchecking the "Use a background service to install updates" box in the Update section of the settings page.
Bug 1658711 Comment 3 Edit History
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There is a way to reproduce the bug I found. And it is possible for Firefox to basically get into this state on its own, so it's possible that this is the reported problem. It should be reproducible by unchecking the "Use a background service to install updates" box in the Update section of the settings page. The remaining STR are the same.