Are you sure it is the relay, if it is trying to move?
I often find a good oiling of the window channels takes the load off the motor and they work a lot better. It nneds to be done regularly.
When servicing customer cars in the past I always oiled the window channels along with door locks and hinges.
These days most garages just seem to give a quick squirt of spray grease to the door hinges if you are lucky.