Try to factory reset that device and see after. Maybe a backup would be beneficial before that, so he won't loose any data.
What about resetting your Network settings:
Step 1: Go to Settings.
Step 2: Scroll down until see General Management and open it.
Step 3: Tap on Reset.
Step 4: Tap on Reset network settings.
Step 5: Tap Reset Settings.
Step 6: Tap Reset settings to confirm it.
Than restart the device.
Can you please go in the Samsung Members app >> Support >> Diagnostics >> and select Bluetooth from the list.
If the test result is normal, then is not a hardware issue, if not, then you need to sent the device to Samsung repair shop.