then it'll be the housing the thing sits in thats not in properly

there were loads of tiny little mods to the panels as the sierra progressed over the years and it's a case of trial and error

if the internal casing fits snug then it will only be the flap itself that is bent out of shape, but they were a bitch to fit in the first place, i had loads of issues when i did this to the estate with cable runs and stuff and it eventually meant a whole strip down of all the panels inside to get it to fit right

there's also the internal handle so you can open it from inside the boot, but not all of them came with them so it's worth hunting for one with it, i used a bit of wire eventually when mine broke