For the electric fence to work, you have to have a good ground. Almost every problem with an electric fence has to do with ground. Either not enough of it because the ground rods are not deep enough, or spread out enough. Three ground rods that re 6 feet deep in the ground and ten feet apart is probably the minimum needed. If you have really bad soil, you can run an additional line from your ground rods along the fence to the halfway point on your fence and add more ground rods there.
You also have to be absolutely positive that your hot wires are not grounding out. Moisture in plants will carry the charge from the wire into the ground. Wire mounted to wood when it gets wet will carry the charge into the ground. You have to have plastic insulators on all your posts, regardless of what they are made of.
I have a cheap tester that just shows voltage with some lights that light up. It goes up to 7,000 volts and as the power surges on the line, the lights will go on and off. It works good enough that I know the fence is working, but nothing like the one they are talking about.
Eddie