So this only happens when there a pushbullet notification and depends on which side of the screen the notification appears at. So if pushbullet is set to show notifications at top-left, then only the top-left split is affected. And if pushbullet notification is set for top-right, only the top-right notification is effected.

Logs included (do I need to click apply after changing the log level or is it automatic?)
Log 10-47am: top-left split affected by top-left pushbullet notification
Log 10-53am: top-right split affected by top-right pushbullet notification