Very high VDD-VSS current

AD5371 data sheet says that IDD max value is 20mA with unloaded channels and this was seen 10+ hours when testing a board. However then AD5371 started drawing upwards of 200mA from VDD and sinking 200mA of current to VSS on startup. This caused thermal shutdown on the connected regulator keeping VDD at 2V, not the intended 16.5V.

When debugging I removed all the connected components including caps, outputs and the regulator and the DAC still pulled a ridiculous amount of current from an externally connected VDD source. Interestingly the floating outputs were oscillating between GND and -300mV at 20Hz which sounds like thermals to me but it doesn't address the issue of the massive current. On thermals, though the case temperature never went above 50C adding further confusion.

The VDD regulator I am using is the LP2951 at 16.5V

The VSS regulator is LM79L08F at -8V

VCC is 3.3V

Vref at 4V

Outputs originally go into op_amps configured as non inverting amplifiers.

Any help in diagnosing this problem would be amazing, I'm completely stumped.

Please let me know any other information you may need.

Thanks