Hi, we acknowledge your query and apologize for the inconvenience caused to you and will surely assist you regarding the same.
We request you to please Check the notification settings for your app. Ensure notifications are turned on and set to the correct sound or vibration.
Restart your device. A restart can often fix temporary software glitches that may be causing problems with notifications.
Please register your concern in Samsung Members Application (Open Samsung Members Application > Support > Tap on error report > Type your query > Send).
Not sure if this will help, but maybe try going into the battery settings for the all and set it to run unrestricted or unoptimized so it can poll more often for notifications.
But I am not sure if my notifications are consistent now since i ever turned off the quickstar in goodlock. But hope it will be always consistent already.