Astra J 1.7 CDTI Tech-Line rear light cluster issue

[AstraCDTI]

Hi all,

I hope someone can assist. Is there anyway to completely open up the rear clusters. 

I have an odd issue where my brake light clear section has snapped in both the rear clusters and rattles around within the larger cluster. I have removed both but after removing the group bulbs out the  rear I cannot find how to disassemble the rest. It looks like anti tamper screws have been used.

Not so much an issue but it keeps on knocking on the brake bulbs and causes intermittent errors when starting the car suggesting rear brakes are at fault. I then have to remove the cluster and secure the bulb back in for a period of time until it happens again. 

Any suggestions on this or is it new cluster time on both sides?

Regards

[Rusty2009]

Only way to fully open them is in the oven.