Trunk locking hatch problem

Ok heres a new problem for me lol

One day in my 99 cavi i went to open the trunk only to find out that the hatch lock had broke on the inside

So I went to the junk yard and pulled another one but I got this great idea to have a electric lock instead of the old one so I could wire it to a switch upfront just to hit the botten or wire it into the alarm

However here is my problem

When i first hooked it up it clicked just fine and opened the trunk but now when i hook it up and slam the trunk down it does not work but it will work sometimes if i pull the trunk closed from the cabel on the inside of the trunk ...

Im lost here really starting to get P#$%ed off at it lol

there is one wire running from it that is 12 volt +

it ground to the body of the trunk

Any ideas? 

Shane

I checked everything 2 or 3 times to make sure and i added a 3rd ground to it just to make sure.

When it works it works fine when it dont work it does nothing no click no nothing

really odd.