In File: Engine\Source\Runtime\Engine\Private\Particles\ParticleBeamModules.cpp
Function: void UParticleModuleTypeDataBeam2::Update(FParticleEmitterInstance* Owner, int32 Offset, float DeltaTime)
// Determine the step size, count, and travelled ratio
BeamData->Direction = BeamData->TargetPoint - BeamData->SourcePoint;
float FullMagnitude = BeamData->Direction.Size();
BeamData->Direction.Normalize();
Note: not consider FullMagnitude is zero. And at line 420:
// Determine the partial trail amount and the steps taken
BeamData->TravelRatio = TrueMagnitude / FullMagnitude;
Hero is a issue divide by zero.