Hello there! I hope this is in the right forum.

I have an animated object which moves from a side to another. I created two spot lights and managed to create a long shadow, but I need the shadow to stay behind the object so I animated the lights translation, creating two keys on the beggining and the end, the problem is that the shadow trembles. I checked and the both lights don't stay always behind the object so I tried to add more keys but the shadow still trembles.
I don't know a lot of maya's technical stuff so I'd really appreciate if someone help or share some helpful info to make she shadow move along with the object without trembling.
Also I've tried with constraints but doesn't work either
I need to create this effect: https://imgur.com/ec4rwbI

Thank you in advance.