Problem with Beam particle. Particle looks flat/thin on most angles.

Hey guys i`m working on a combat system prototype, one of the features is a beam that goes from the player to the target, my problem is that for some reason my beam (the particle) looks flat on some angles as the camera moves. i do believe its a problem on my Beam particle.

A .gif where you can see the problem.

Any ideas?

PS: sorry for the poor english.