I have an 05 Signum and it used to have 2 electric faults before I found this fix.
Faults
- The Boot popped when unlocking the car from an 'alarm armed' state. But not enough to actually open, just rattle. I had to force it shut with .5 cm of travel, then it would unlock fine
- 12v sockets weren't working
Fix
I replaced the 30A fuse for the 12v sockets and it's fixed BOTH issues.
So if you have the boot popping issue, check all the fuses as something 'unrelated' may actually be affecting it.