First photo suggest that power cables of spindle are far away from any other cables - thats good. What i don't like - spindle uses single lead cables and they are far from each other creating large "loop" - bind both cables together or - even better - twist together (create "twisted pair" ). Check if spindle has EMI suppression capacitor - without it DC motor will generate a lot of noise. Check if there is electrical connection between spindle power and machine chassis (baaad thing).
No guarantee it will help - these problems can be tricky to solve.