Noise in the analog input when using MKR CAN shield to control a motor

I am trying to control a motor unit (with its own control circuit and microcontrollers) using Arduino MKR ZERO. The control signals are acquired through a voltage sensor using analogReadFast(A1), which control the motor through the MKR CAN shield. The motor unit is powered by 230V electrical supply.

When the Arduino board was powered by the PC, the system worked totally fine. However, 25Hz noise occurs on the analog input signals (A1) when I powered the Arduino by a power bank instead. The noise disappeared when I turned off the motor unit.

May I ask if anyone knows the reasons for this issue or has any suggestions to fix it? Is it possible if the input signals are affected by the CAN bus?

All Arduino boards are not as isolated from noise as an industrial unit would be so extra care must be taken.
Shielded cables, Ferrites, Capacitors, snubbers, etc etc must be used to avoid introduction of noise.

You didn't include any pics of schematics which may aid people who want to help.

Could you also take a few moments to Learn How To Use The Forum.
Other general help and troubleshooting advice can be found here.
It will help you get the best out of the forum in the future.