Hi JL, I'm a software developer so i know sometimes is weird! :D
In anycase , i've 3 modules from Cockpit Sonic :
1. FCU, backlight don't work from B31 (in B30 it's ok)
2. RMP , backlight don't work from B31 (in B30 it's ok)
3. ECAM , the backlight work but it is always turned on because it turn on when i turn on the psu
Regards.