Thanks for the advice. I unpaired the earbuds, removed my ~/.config/pulse directory, rebooted, then used bluetoothctl to trust, pair, and connect them again. It seems to have worked (they have been connected for about 10 minutes and have not disconnected yet), but I am still having a few issues which I did not have under Jessie:
1. The left/right channels are swapped (according to the speaker test in the Gnome sound settings)
2. The sound frequently becomes choppy and/or cuts out for several seconds. I am sitting about 3 feet from the USB Bluetooth adapter plugged into the PC, and it was always fine before.
Any ideas on fixing the channels and sound quality?
Thanks!