Electric fields really like to be linear, but the described anomalous effects are highly nonlinear
The non-anomalous effects, like high electric field readings, could linear
The wall only effects living things- birds, bugs and people
My guess is that the wall is mediated by the nervous system and muscle contractions, which unlike electrostatic forces, are free to have thresholds, nonlinearities, and psychological effects. Basically, everyone involved was getting zapped all to heck and any subjective experience is plausible downstream of taking a megavolt to the spine
If that were the case, wouldn't people just fall down, and possibly die from their heart stopping? Instead of feeling an invisible wall that they can walk away from.