Many things cause it , air pressure, fan adjustment, material adjustment, going to slow or fast with the paint gun.
I will give you some help on how to solve the tiger
stripe problem, Lacquer is suppose to be thinned up to 150% , then with each coat cross hatch the pattern, go one way once, then cross ways the next this should help.

Another thing is if your fluid tip , needle, and air cap can be wore out, as this can be a problem too.

SprayTech