I have downloaded 2018-11-13 Stretch and used the new version of Etcher to flash a 16GB microSD card. Upon first power-up, I do "sudo apt-get update" and "sudo apt-get dist-upgrade". I can pair a Bluetooth Speaker by clicking the Bluetooth icon in the system tray, selecting "Add device..." from the menu, waiting for my device to appear, selecting it and clicking the "Pair" button. I am then notified that pairing is successful.
After seeing several posts say that Bluetooth audio works very well with Chromium, I always used music on YouTube as the audio source when dealing with Bluetooth. I used HDMI for sending the music (along with the video signal) to my TV where I can see and hear the stream fine. I then right-click on the Speaker Icon in the system tray, which pops up a menu that has 3 options to choose from (Analog, HDMI, and my Bluetooth Speaker), and I click on my Bluetooth Speaker. My Bluetooth Speaker connects and indicates that it is connected, but no sound. Instead, the music video keeps on playing on my TV without interruption. Since I have nothing plugged into the analog jack on the RPi3, switching from "HDMI" to "Analog" kills the sound as would be expected. The sound then resumes when switching from "Analog" back to "HDMI". But whenever my Bluetooth Speaker`connects (either from "Analog" or "HDMI"), the sound (or silence) doesn't change.
I have used 2 different devices as Bluetooth Speakers (both of which work fine with either a smartTV or PC transmitting), but neither make any sound when I use my RPi3. I know they connect successfully because one has an LED which turns on, and because I can hear the other one say "connected" in the ear buds. I also know that the onboard Bluetooth on the Rpi3 works because I can use my Bluetooth mouse and my Bluetooth keyboard (both at the same time).
I have repeated this entire process three times, starting with a fresh download each time, but still no sound. I didn't set up or install anything before trying Bluetooth the last two times. But now what happens is the Bluetooth Icon in the system tray has zero width, making it invisible. It's still there between the Network Icon and the Speaker Icon because I can still click it and the menu pops up, but only if I move the mouse pointer to just the right sliver of screen between the other two icons. I'm starting to think I might have a hardware problem on the RPi3 board, because of how persistent the problem is and because I've been scouring these forums and also at the Raspberry Pi Stack Exchange thingy (I DARE NOT call it a FORUM!!!!), and I haven't found anyone with this problem. If it were caused by an OS bug, I would expect to see lots of people with the same problem.
I have seen many posts and tutorials use the CLI to get Bluetooth audio to work, but since the GUI can now (supposedly) enable Bluetooth audio "out of the box", and is so much simpler that the CLI, I have not tried using the CLI anymore. Since the GUI functionality is still rather new, I haven't seen a whole lot on the process; I assume that not much news means not many problems. So I'm getting to the point where I'm suspecting some kind of bizarre hardware conspiracy theory is to blame! If it's not hardware, then why am I the only one having this nightmare? I've even begun to consider putting a circle of chicken bones around my Pi!