Message+ issues repeat notifications

[Jimmy_W]

The Message+ app on my S8+ is set to present a notification sound and open a box on the screen when I receive a message. Those features work, but after about one minute, the notification sound repeats. I have nothing set to repeat notifications, and it doesn't matter which sound I choose. Moreover, I've found that this repeated sound notification doesn't happen all the time. Anyone have a clue as to why the notification repeats? Thanks.