Issues Controlling BBC M17H DC pancake motor with Parker 512C

[slawekgonet]

Hey,

I'm attempting to driver BBC M17H DC axial flow servo motor with Parker/Eurother 512C speed controller and I am facing some issues.
I've set the controller up with autotransformer to supply it with 230VAC as AUX and 90VAC MAINS (motor is rated for 105VDC nominal).

Unfortunately, motor is running extremely choppy and in interrupted fashion - and is not able to spin at low RPM at all.

https://youtube.com/shorts/lxh0J69C-WI?feature=share

Do you have any ideas what can be wrong? How to even start debugging this issue?

Thanks!