this is a new one on me.
I was carrying a couple of sticks to throw across the fence out of the yard. Heard the electric fence clicking at an insulator. Could not at first see any problem but moved the wire with a stick and it would stop clicking momentarily. Now, I had just had chicken litter spread, actually the pure stuff from a layer operation. Due to humidity and the layer operator not having it moved often enough, the manure was soupy and the spreader truck had slung a wad against the insulator and it had spread down to the next barbed wire which was nailed to the post. Scraped the insulaor clean and the clicking stopped.
KEH