Fenix 5x+ version 18 backlight stuck on

After upgrading the software to v18, my Fenix 5x+ backlight gets stuck on at full brightness. This kills the battery very quickly.

Pressing the backlight button does nothing. Reset to default does nothing. The only thing that turns is off is powering it off for a couple minutes then back on. But the backlight eventually turns itself on for whatever reason and does not then off again. 

Is there a resolution to this? The only immediate one is to force a downgrade of software but am not sure if that's possible.