Welcome to LinuxCNC.org

I believe I'm trying to run these drives in torque (current) mode. The drive is AMC 30a8.

www.a-m-c.com/download/manual/AMC_Analog...es_InstallManual.pdf - Manual
www.a-m-c.com/download/support/an-007.pdf - Running brushed motors
www.a-m-c.com/download/datasheet/b30a8.pdf - Data sheet

I confirmed that I'm in PWM gen mode 2.

I would set your FE range a little larger and set your I=0, D=0 and P = .1 or so
to first verify proper feedback direction.

There are a couple of possibilities here for what appears to be runaway, one is feedback direction. the other one is oscillation because the PID loop gains are starting out too high

By setting a low P gain. proper feedback direction can be verified

If this does not work, I would break the feedback loop (say disconnect the drives from the analog out) and verify that the analog outpu does the expected thing when LinuxCNC is started and the motor shafts are rotated away from their starting positions (the analog voltage should be proportional to the distance from the starting position (and the polarity should match the direction of motion from the starting position)

Update:

I had one of the pots on the drive turned the wrong way. With that corrected when I bring the machine out of estop the axis does not move. The motor is not yet holding the axis stationary but I checked the voltage between between + REF IN and - REF IN and I see a voltage which increases as I turn the handwheel. If I reverse the direction rotation the voltage goes back to 0 and then negative which seems correct.

I'm concluding that my drive set up is still not correct. I'll go back over the manuals to see if I can find any more set up errors.

Can you verify that the REF inputs change in such a way as to
drive the motor in the reverse direction of the displacement?

(This is the correct negative feedback configuration)

The motor isnt driving or holding the axis so I'm not sure how to verify that. The absolute value of the ref signal increases as I turn the handle in either direction.

is the drive enabled?
If a non zero input does not drive the motor you need to solve this first