Victim2---I use pads with my fungus zapper and found having the current more easily directed versus having to run through my whole body helped immensely.
I was zapping with the pads very similarly as you describe for my liver tumor. I think the pads are designed to deal with electricity, and I use them for my e-stim unit for muscle stimulation all the time and they work great for that, and haven't melted a single pad.
The e-stim is a much stronger current, so if they did melt, that machine would be the one to do so, I'd think. I wondering if perhaps they're just 'shedding' which, like any adhesive will if you leave it on a long time. I've had a bit of that the times I left it on longer.
The current only seems to reduce significantly when the pads get worn, and as parazapper notes, you do need to keep replacing the pads as they get unsticky after a while and don't make the needed contact, and, at least for the fungus frequency, it might start stinging/doing little electrical burns--which says to me, the contact area isn't sufficient any more, which may be what your burning/stinging was about, versus a 'melting' pad.
Also if you jerk them around by pulling them off using the wire part versus the edge of the pad, you can break the little wires inside. And yeah, that causes the broken wire ends to poke thru the gel and sting/burn like crazy.
I've never gotten that with new pads though. They run under 6 bucks for a set of four, so if you need a lot, it can add up. But I don't move the zapper pads around as much as the e-stim, and I can get a couple months or more out of one set, although it does get into that stinging range at times.
I think even if they don't carry the current as well though, it definitely helps get the current going thru the right place, versus the shotgun approach of the more hand held type, which the pads won't do. You have to aim it more carefully, like a 9mm.
And there seem to be times for both approaches. I think it's better to do shotgun style when there may be lots of places where
parasites are or you aren't sure where, but if it's like the fungus aka cancer, the pads set as you described got the tumor extremely well, but didn't stop the fungus from migrating to my hip joint, but once I focused the current there (for a while I focused it in both places), it did, but probably wouldn't have helped with the liver tumor if I'd only focused it on the hip joint.
At least that's my observational theory, not terribly technical, I know. :)