I am an expert on this subject! Not on purpose....but I have dealt with EXACTLY this problem. I have two puppies and am the official underground fence installer, fixer and trainer.
We are on rural acreage and can't use a regular fence. We also have lots of garden areas that doodles would wreck in no time. The neighbors keep sheep - dogs here can be shot if found running free. We installed an underground fence when the pups were about 5 months old.
Grace figured out that she could jump high enough at the boundary that she could actually avoid the static altogether. It was really funny seeing her back up and take a flying leap right over this imaginary line! But it was extremely frustrating too. Over the course of months we tried all sorts of things, including shaving the hair where the probes are, getting longer probes, increasing the boundary width, etc. Everything helped a little, as did, of course, training with a lead. But one day I found Grace in the yard chewing up the collar and the receiver unit. We almost gave up.
But we couldn't, so as a final effort I ordered the "stubborn dog" receiver. It is LESS expensive than the other ones and it delivers a vibration and an annoying tone before it "zaps". The static is a little stronger, too. It worked wonders and we have had NO problems with doodles getting out since then. They have about 3 acres to run free in and the gardens are outside the perimeter, so no more torn up plants and my doods are safe.
I know a lot of folks have a problem with the idea of the static correction, but I used it on myself before I allowed it on my puppies. It is quite unpleasant, but not exactly painful. In any case it's better than the doods getting into the sheep or out onto the road.
My advice is to keep working with it. I rearranged the wire and extended it several times before I got it just right, but now we never even think about it. (Except last week my husband hit the line with the tractor! I have a little repair kit I keep ready all the time)
Sorry this is so long. Sometimes I DO run on...