Well, first check the battery voltage. The spoiler coming up on it's own is a sign of low voltage.
You should see 12.1-12.3 volts with everything off, 14.2 - 14.5 with the engine running.

Removing fuse #20 may have other adverse effects, it does supply power to the BCM for the spoiler motor drive, but may well be the source of power for other BCM functions.