You might want to put some logging in your event listener to debug this
Log::info('Event fired', [
'request_id' => request()->id() ?? uniqid(),
'path' => request()->path(),
'server' => gethostname(),
'memory' => memory_get_usage(true)
]);
additionally might want to check that there are no multiple event registration on your EventServiceProvider
Also can you check that you dont have multiple instance of the app service plan deployed ?