Central Locking Actuator Installion Problems =/

[ED Incarnate]

Hey guys,
I've got a 93 dec, ED and the actuator on the left front hand side passenger side decided to pack up the other day. picked a spare off the wrecker for $25.

new actuator functions fine, its exactly the same as the former actuator however when fitting it to the car i used bolts instead of rivets to attach it to ensure it aligns up correctly.

I've screwed it in and locked the car however when the actuator arm actually goes down it doesn't quite go the full extension and consquently goes back up the original unlock position, however if i unscrew the actuator and move it up (physically hold it) a few mm from the original drill holes it functions fine...

do i need to put on a new piece of sheet metal and rescrew the holes so it functions correctly, i mean its exactly the same how can it not physically get the required length so that it gets in the lock position? I am still using the older existing steel rod that attachs to the actuator as its exactly the same length as the one it came with

this is really frustrating any help would be greatly appreciated. thanks