plate and pid controller kits.

Hey guys , long time since I've posted but I had a question that I've been having some difficulty getting an answer to.
I recently bought a plate and controller set up tO attach to my press. The pid had the whole aerial plug set up to the plates. Seemed pretty straight forward although there were no instructions of any kind included.
When the shipment came in, before plugging in the plates to the pid, i plugged the pid into the wall to make sure it would turn on and everything. My hand was on the pid when i plugged it in and it electrocuted me. Not seriously enough to go to the er. But bad enough to hurt real bad and disorient me. I immediately unplugged it.
I then later wore rubber insulated gloves and Plugged in the plates to the pid. Then i plugged the pid into the wall. I hit the on switch, everything seemed to be working. I set the temp to 200f, and waited for it to heat up. Then as it was heating (one of the plates was about 1.5 inches from the box) the box and the closer plate to the box arced out bad enough to melt a small piece of the 7/8" aluminum plate.. just a damaged dot on the edge.

My question is why did this happen? Is it normal for closed loop circuits to do this? If so what precautions could i take in the future?
Is it likely to be a manufacturer error?
Was it user error (i.e. something im over looking)?
Just seems to me if it was a common issue i wouldnt have so much trouble finding info on it.

Thanks guys im sure whatever you can add to the subject will be helpful and appreciated.

It sounds like you have an un-grounded system.

The arching out, is probably where the current leak was, suggesting poor insulation or insulation not suitable for high temperatures.

Thanks for the reply fade. The aerials to the plates look like they are grounded to the plates between the heating elements.
However I opened up the pid box, and found a ground wire just hanging in there. Unimpressed with the company distributing this product overall.

So I had eBay step in because the seller wasn't getting back to me.about return info. Within 12 hours I had a full refund and was told I do not need to ship it back.

So ultimately I ended up with two aerial plug aluminum press plates for just the cost of being electrocuted...haha.

So I'll probably just end up buying a dual pid from a reputable source and make. Who knows though may just wire one up myself. At least then I know it'll be properly grounded.