Add-on install failure in 60.2.1

[wsmwk (Vseerror)]

Today we have cases of two add-ons which are shown in ATN as being compatible with 60.0 but fail to install for some users

• https://addons.thunderbird.net/en-US/thunderbird/addon/theme-font-size-changer-fixed/ failed to install per https://support.mozilla.org/en-US/questions/1235630#answer-116
• https://addons.thunderbird.net/en-US/thunderbird/addon/unread-badge/ failed to install per https://support.mozilla.org/en-US/questions/1236088#answer-1161116

However, two others (myself included) successfully installed these add-ons in 60.2.1.

What might be causing this? Wild theories accepted

[wsmwk (Vseerror)]

In a tiny bit of testing in a newish profile

• successfully installs https://addons.thunderbird.net/en-US/thunderbird/addon/theme-font-size-changer-fixed/ em:minVersion58.0</em:minVersion> em:maxVersion60.0</em:maxVersion>

• reliably fails install https://addons.thunderbird.net/en-US/thunderbird/addon/unread-badge/
  em:minVersion10.0</em:minVersion>
  em:maxVersion60.0</em:maxVersion>

i.e. both have maxversion 60.0

[wsmwk (Vseerror)]

filed https://bugzilla.mozilla.org/show_bug.cgi?id=1496535

[wsmwk (Vseerror)]

The bug is resolved and updates for 60.2.1 are flowing