What could be causing ZVS imbalance?
Thank you to everyone that commented.

Your comments were taken on board and I have since looked into this more fully. I built my own circuit to drive this load and that is what the scopes are from. The coil was 7 turns of 5mm copper, with 2uH capacitance added. My driver did not blow up but because I was having issues and have quite complex schematics I reverted to sticking a mazilli driver on it to see what would happen and determine if it was my circuit or the load (Mazilli driver from - http://gaugeboson.com/electronics/high_voltage.html)

When the Mazilli driver was connected it would heat rapidly and blow in about a minute @ 150-200w. The parasitics pictured were greater in amplitude than the sine in the case of the mazilli.

Anyway I have found the answer after about 18 hours of troubleshooting, 5 mosfets and 2 burnt caps later, and post it as it may help some people using Mazilli drivers for their tesla coils/ etc as I have done in the past

Stray inductance.

If your having a similar issue with your flyback drivers as I was having with my own circuit, and then the mazilli, it may help to place larger capacitance directly across (i.e. as close as possible) to the drains of the fets. This stopped the Mazilli blowing up and allowed me to then attach and troubleshoot my circuit (well the load, as the circuit operates fine on other loads). From testing I would say that the capacitance at this location should be at least 1/3rd of the total capacitance of the tank to eliminate the issue, at least in my case.

I can only fathom that the inductance between the load and the fets was setting up another resonant tank that resonated upon switching the fets due to Miller effect. In the case of the mazilli, which relies upon the gates being pulled low by the fet that's on, it would resonate all over the place in and out of the linear region, thus destruction. On the mazilli I got as much as 8mhz oscillations occurring. I am not sure if coupling of the coil to the circuit could cause such interference or not?

Anyway, thank you for the input of others and hope that inadvertently this question may assist someone experiencing parasitics in their own ZVS. I still don't know why this load was so troublesome as the leads are very short but will re-design it more appropriately moving forward.