SC2Mapster

From the faults it is some hosting issue in that the same actor is being shared between  multiple casters/instances and being orphaned causing it to drop off the host.

In such cases I try to avoid the blizzard method and find an alternative.

I would use a Create Persistent effect combined with a Location Range validator. The initial effect of the persistent adds a buff and the final removes it. The persistent can then be used for beam actor creation and destruction. The buff can stack infinitely but is limited to one per caster and as an initial effect adds a second buff that can only have one stack and is validated to be removed if the other buff is <1 stack. This way the periodic search for applying the persistent can be validated to not apply persistents to units that already have a buff from the caster and even disable the search if there are no valid targets.