I don't trap groundhogs, so I am not really the best to answer your question. All I can do is offer generalities that apply to setting body grips - which I set a lot of.
What do you mean by "it was pulled outside the hole." You are setting in a hole? You are not setting at the entrance of the hole?
If you are setting IN the hole the animal might be trying to go under the bottom trap jaws.
Given the success you are not having, I would definitely try a different trigger configuration. Doing the same thing is giving you the same result. "L" shape is usually a good shape when trying to get something bigger in a bodygrip. If the dog is on the bottom, be certain it has room to fire properly.
You're welcome for the help. I'm hoping that someone with actual groundhog trapping experience chimes in.