Hi,
What does it mean? You are sending different speed setpoint and motor doesn’t spin stably at any setpoint or the motor stalls when the speed exceeds particular value?
I suggest you to perform motor identification first. Maybe, the motor parameters have been changed.
If it doesn’t help try to tune m.flux_linkage as it described in the Quick Start Guide.
As I can see from your plots, the motor doesn’t spin up confidently. It seems like the thruster requires a quite big torque at low speeds. The current is not enough to maintain its rotation. Increase the m.spup_curr_end parameter. You can read more about the spinup tuning in the Quick Start Guide. It would also be nice to set the m.min_current parameter equal to m.spup_curr_end.
Finally, as I can see from the parameters list, the m.voltage_ramp parameter is too small. If you control Myxa in RPM control mode, set it to the maximum value in order not to decrease the bandwidth. The bandwidth in RPM control mode should be constrained by acceleration/deceleration rates and speed controller. As I can see you have set the control mode parameter to RPM control mode in RCPWM interface settings.