I built that kit recently, I think I put 4 coats of testers decal bonder on the sheet to get the decals to stay together. I tested one of the other colour of stripes in between each coat. That sheet was fragile even when it was new.
I have often had issues with the windshield, dashboard interface on that kit, causing that issue. I trimmed the bottom of the windshield on one of them
Another thing that changed on these kits was the roll cage. In the stp and pennzoil kits more bars where added around the drivers seat, the 4th gen firebird had a narrower cage, in the current kit the cage is still the narrow one.