Why does my audio stop playing through Bluetooth?

Recently my Samsung Galaxy S8+ will stop playing randomly switch my audio from the Bluetooth device to the phone's speaker. I have two speakers and two earphones and neither seem to work properly. Also, it happens with any app that has audio. There is not consistent time frame, and will sometimes not happen for an hour or so, or will happen two or three times in a minute. When I reselect the device via the SmartThings notification tool, the audio will switch back to Bluetooth. Can someone give an idea of how to fix this?

I just started having the problem today on my LG G6. I was listening to audio through my bluetooth headphones, when suddenly the sound was coming from the phone's speaker, and not my headphones. After the second time it happened, about an hour later, I rebooted the phone. Then it occurred a third time. I'm not losing the bluetooth connection-- there's a notification bar on the lock screen "Select the device for media audio", and I can choose my headphones or the phone. I'm able to switch it back by selecting the headphones there.

I spend hours a day at work listening to various audio sources from my phone on my bluetooth headset, and have never had this problem before today. Now it's happening frequently. When it happens my phone is laying on my desk, and not being touched.