Trinity reported this error earlier:

2x totalRP3\core\impl\configuration.lua:80: Unknown config key: MAKE_SURE_BROADCAST_CHANNEL_IS_LAST
[string "=[C]"]: in function `assert'
[string "@totalRP3\core\impl\configuration.lua"]:80: in function <totalRP3\core\impl\configuration.lua:79>
[string "@totalRP3\core\impl\communication_protocol_broadcast.lua"]:274: in function <...alRP3\core\impl\communication_protocol_broadcast.lua:273>
[string "=[C]"]: in function `xpcall'
[string "@totalRP3\libs\Ellyb\Tools\EventsDispatcher.lua"]:74: in function `TriggerEvent'
[string "@totalRP3\libs\Ellyb\Tools\GameEvents.lua"]:43: in function <...facetotalRP3\libs\Ellyb\Tools\GameEvents.lua:41>

As we've not changed that key in any way for 9.0, and no one else has seen the issue, I did a bit of investigating and my conclusion is that we've RNG'd our way into this situation.

The use of the config key in the broadcast protocol stuff is within moveBroadcastChannelToTheBottomOfTheList, which has four potential callsites - three are game event based, and one is after a ticker elapses during the initial loading workflow. Odds are we ended up receiving one of the game events before our workflow executed, which seems unlikely but anything's possible I guess.

My suggestion would be that we delay registering the game events until we've reached step 2 of the broadcast initialization - when we've connected to the channel. That way they definitely can't fire early on us.