Haj Raj,

using snubbers across relais contacts will solve your problem very probably.

But snubbers are better located directly at motor, if possible! Because this would prevent cables from transporting switching noise to your board, from resonating and from radiating!! Also common mode noise is highly minimzed.
Snubber circuit sitting directly at motor is often called 'motor filter'.

I have seen many driver boards not having any Faraday cage but nevertheless working correctly. So, it only depends on how good suppressing of switching noise can be achieved.

Switching inductive loads without 'snubbering' is always deadly!!

Kai