One comment I had regarding the horse touching their nose to the fence to test it....
Get a fence tester with multiple neon lights on it to check your voltage, it must be really low if the horse will do that. I bought ours for less than $10 at the local farm supply store.
Maybe your ground rod isn't making good contact, maybe your line from charger to fence is corroded, maybe the fence charger is just old and weak.
But..an electric fence should zap them hard enough they don't even think of trying to get thru it should the power go out or the fence ground out a bit.
Our fence ( and I am certainly no expert at electric fences ) tests at 9000+ volts, and the animals won't even think of getting in contact with it. I have a Dexter bull that would just walk thru the fence before I got it hot, now he respects it and stays in.
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