What kind of oil do you run? and is it worse when the trike is warm (operating temp) or Cold? What can happen is sometimes the clutches can swell due to some contaminate in the oil, this can usually be resolved by taking the clutch apart and using some brake cleaner to clean off the clutches.
If this is something that happens all the time, and the clutch has some miles on it, I would be more inclined to say perhapps the metal plates between the clutches have started to warp and need replacement.
Hope that helps some
Josh
84 200x (going through Resto)