Only 3.4 volts going to starter (SOLVED?)

Hello all, my 2016 Yukon is having some odd electrical problem

Started out not starting, just a click. After a couple of tries it starts, thought it was the starter. I installed a new starter and it happened again, I reinstalled the old starter because the new starter made an odd noise when starting.

This morning went out to start it and it did the click no start, this time no power to anything. Messed with the neg battery cable since I removed it when I was replacing the starter. There was a little heat near the end of the ground cable at the battery. After a little bit I heard system’s wake up, got it started and went to work, fun not.

Home from work cleaned the two grounds from the battery, nothing looked bad, battery post was cleaned after doing the starter.

Now I am only getting 3.9 volts at the starter. Battery has 12.5v and all the wires coming off the fuse block leaving the the battery also has 12.5v.

Nothing inside comes on as well. All I did was clean the grounds.

Ohms on the ground cable are 0.0

Any pointers on where to look would be great, thank you all.

I believe it is the negative battery cable.
Ordered, I will see, stay tuned

Knowledge is power. Do a voltage drop test to confirm:

So far it is good. New neg battery cable and old starter.