I bought a used hot tub off of craigslist and am setting it up to make sure everything works. I connected the wiring from my old hot tub, however, as soon as I flip the GFCI, it trips. I disconnected the heater and it doesn't trip. I did the ohm testing and it is 11.5 when I test the leads and 0 when I test the lead to the outer sheath. I believe that indicates everything is OK. However, do I ignore the testing at this point and just assume it's a heater element issue since that is definitely what is causing the trip? There is some corrosion at the top of the element near the leads...could that be causing the short? I've attached a picture of the leads.