Unusual crankshaft position sensor waveform

I have an 2.4 VVT ecotec out of a 2010 pontiac G6 for a dune buggy. Full engine teardown, gave block heads and crank to a machine shop. Reassembled with all brand new seals and sensors. Custom harness and tuned computer from an aftermarket shop. When cranking, it sounds fine cranking for the most part. Sometimes it acts like its trying to start and it did catch for about a second then hard stops. Borrowed a solus scan tool and it is getting a crankshaft position sensor error. It is also producing a weird waveform (see photo). In the photo, the drop is when I stopped cranking. The computer and harness check out, as we put it on another engine and it starts right up and runs no issues. I bought a second brand new sensor (both are standard brand) and tried that. It does the same thing with an occasional backfire. Still throwing the code. Any ideas?   

What exactly is the code that is setting?
Hard cranking and backfire sounds like the timing could be off.
I do want to point out that what you have there is not a waveform, it is graphed, processed data from the PCM on a scan tool. A waveform is obtained with an oscilloscope. It may sound like splitting hairs, but it is important to know the difference.

Hi Noah. The code is a P0335. What's weird is the back firing only started after trying a second new sensor. I guess it's always possible the first new sensor could be faulty. I'm planning to pull the timing cover this weekend to double check. At this point I hope its the timing because only other thing I could think is something with the reluctor wheel, but I'd have to pull the crank out again.