Bluetooth doesn't work after resuming from sleep, Ubuntu 18.04 LTS

update bluez to >=5.28.2

18.04 ships with a buggy bluez package for now; newer version is available from this PPA: https://launchpad.net/~bluetooth/+archive/ubuntu/bluez:

sudo add-apt-repository ppa:bluetooth/bluez
sudo apt install bluez

---

workaround for buggy Bluetooth applet (Unity specific?)

This is probably the issue @solstice mentioned - BT menu applet doesn't let me enable Bluetooth after resuming from sleep. No matter if the toggle switch is off or on, the BT icon is disabled, and rfkill output doesn't change:

$ rfkill list
0: phy0: Wireless LAN
    Soft blocked: no
    Hard blocked: no
12: hci0: Bluetooth
    Soft blocked: no
    Hard blocked: no

You can toggle BT manually by running (substitute your own ID):

rfkill block 12
rfkill unblock 12

and BT applet should pick it up correctly now. At this point, you should be able to connect to your devices. For now I've hacked it together using a script that does this automatically after resume:

$ cat /lib/systemd/system-sleep/bt
#!/bin/sh

case $1 in
  post)
    sleep 5
    rfkill block `rfkill list | grep hci | cut -d: -f1`
    sleep 1
    rfkill unblock `rfkill list | grep hci | cut -d: -f1`
    ;;
esac

The ID number next to hci0 in rfkill list output seems to increment after every suspend/resume. Disabling/enabling BT using the BT menu should change the output ('soft blocked: yes' for BT disabled via menu), but it doesn't. My guess is that the applet remembers the wrong device ID and is thus trying to enable a device that no longer exists.

For me this problem can be resolved by running

sudo service bluetooth restart

after waking from sleep

I run 19.04 and have this issue. I have a BT mouse so it really is annoying.

To enhanced @hinxnz answer:

Open an new file:

sudo nano /lib/systemd/system-sleep/bt

Paste in this script:

#!/bin/sh

case $1 in
  post)
    modprobe -r btusb
    sleep 1
    service bluetooth restart
    sleep 1
    modprobe btusb
    ;;
esac

An finally make it executable

chmod +x /lib/systemd/system-sleep/bt