I experience the same issue with the 8.1.90 as with the 8.1.100 version (Generic x86 verision)
Addon won't start after reboot. I have to disable and enable it to start working properly.
-- Logs begin at Thu 2017-06-08 21:21:20 CEST, end at Thu 2017-06-08 21:22:46 CE
Jun 08 21:21:21 LibreELEC systemd: Started librespot.
Jun 08 21:21:21 LibreELEC sh: Unable to activate an audio interface on Gene