"Bluetooth: not available"
Recently, every few days when waking my 2015 MBP, it does not connect to my wireless keyboard. Trying to reconnect it, I often get the error "Bluetooth: not available". Sometimes sleeping the computer brings back Bluetooth, other times I have to restart the computer. The problem seems to be worse since pairing the keyboard with a Mac mini a few weeks ago, but it started before that. I searched Apple Support, found nothing relevant. Google search turns up articles recommending deleting /Library/Preferences/com.apple.Bluetooth.plist, or resetting SMC, but these do not solve the problem permanently. Is this a hardware problem? Appreciate knowledgeable advice.
MacBook Pro, macOS Sierra (10.12.6), 2015 MacBook Pro