Jake,
I am not an expert here, just designing a sheep fence right now. So free advice, may be worth what you pay for it.
What is your intent on the fence? Keep sheep in or predators out? Flighty sheep or domesticated sheep? What predators?
Big predators or exclusion of other animals needs big voltage. I have a small (I think)
solar 0.6J system for animal retaining. Due to the fact that this goes in fairly high forage I'm ok with >4k V. This is the mobile paddock, and is not really for large predator protection- that's the perimeter fence.
Perimeter is grid powered, and aiming for >9k V. This with intermittent charge
should keep weeds from growing into it.
Based on the presentation, this is bad contact to the fence, really low resistance short or a faulty charger. 0.1kV seems really low even with heavy weed pressure. Check output directly from the charger, then isolate the fence in a weed free area and dry-test it if you have a moveable system (sounds like you don't have that). Since yours is on fenceposts I guess see if your can isolate different runs with a car battery and portable charger and see which one is your low resistance run.
If you can get your hands on one, you can use a clamp-type tester to see roughly where you are losing if you can isolate as you go along, adding runs. I have one that is very portable. Unfortunately for troubleshooting there is no way I know of other than breaking into units and testing each added section.