2003cl55

I have a 2003 cl55
3rd brakelight was leaking into the trunk.
So I tried to replace it... I just broke my 3rd brand new brake light.
I can't get the lens to lock completely in place.
The center, left and right clips lock in fine. But as soon as I get to the end clips (left and right) they don't lock in ... I press harder... They don't lock in.... I press harder ... The end snaps off .... I charge another 150 on my credit card... Then Repeat the same process 3x and counting.
Is there some trick to this?
I can't be the only one who
Had this trouble.... Can I?
(The trunk lid has never been damaged or repaired, so the opening is to spec)
Help! (before I silicone the opening and screw a trailer light to my trunk lid... Lol)