produces bug with emitter

private static Emitter engineFire(AssetManager assetManager, Geometry geom) {
                Emitter emitter = new Emitter();
                emitter.setName("engine fire- " + geom.getName());

                PolarizedMeshEmitterShape shape = new PolarizedMeshEmitterShape();
                //shape.setPolarity(new Vector3f(0, .73159f, -1));
                shape.setPolarity(new Vector3f(-0.02f, 1, 1.1f));
                shape.setPolarityWeight(.015f, 0.9f);
                shape.setShape(geom.getMesh());
                emitter.setShape(shape);

                //emitter.setParticleType(ParticleDataImpostorMesh.class); // For particles other than the default quad impostor based particle
                emitter.setMaxParticles(100);
                emitter.setEmissionsPerSecond(30);
                emitter.setParticlesPerEmission(1);
                emitter.setDirectionType(MeshEmitterShape.DirectionType.Normal);
                emitter.setBillboardMode(Emitter.BillboardMode.Camera);
                emitter.setForceMinMax(-.1f, 0);
                emitter.setLifeMinMax(1f, 2);

                emitter.setUseRandomEmissionPoint(true);
                emitter.setParticlesFollowEmitter(false);

                emitter.setSprite("Effects/Explosion/flame.png", 2, 2);
                Material mat = new Material(assetManager, "Common/MatDefs/Misc/Particle.j3md");
                mat.getAdditionalRenderState().setFaceCullMode(RenderState.FaceCullMode.Off);
                mat.getAdditionalRenderState().setBlendMode(RenderState.BlendMode.AlphaAdditive);
                emitter.setMaterial(mat, "Texture", true);

                //e1.setEmitterTestMode(true, true); // Enabling the test mode shapes (emitter shape, particle mesh)

                ColorInfluencer c = new ColorInfluencer();
                c.addColor(ColorRGBA.Yellow);
                c.addColor(ColorRGBA.Blue.mult(ColorRGBA.Yellow));
                c.addColor(ColorRGBA.Red);
                c.setFixedDuration(0.35f);
                emitter.addInfluencer(c);

                AlphaInfluencer a = new AlphaInfluencer();
                a.addAlpha(1.0f, Interpolation.linear);
                a.addAlpha(0.1698f, Interpolation.linear);
                emitter.addInfluencer(a);

                SizeInfluencer s = new SizeInfluencer();
                s.addSize(new Vector3f(0.5f, 0.6f, 0.5f));
                s.addSize(new Vector3f(.5f, 1f, .5f));
                s.setUseRandomSize(true);
                s.setRandomSizeTolerance(.35f);
                s.setFixedDuration(1);
                emitter.addInfluencer(s);

                RotationInfluencer r = new RotationInfluencer();
                r.addRotationSpeed(new Vector3f(0.0f, 0.0f, 0.0f));
                r.setUseRandomStartRotation(false, false, false);
                r.setUseRandomDirection(true);
                r.setUseRandomSpeed(true);
                emitter.addInfluencer(r);

                GravityInfluencer g = new GravityInfluencer();
                g.setGravity(new Vector3f(0.0f, -1, 0.0f));
                g.setMagnitude(0.015f);
                emitter.addInfluencer(g);

                return emitter;
        }

        private static Emitter engineSmoke(AssetManager assetManager, Geometry geom) {
                Emitter e1 = new Emitter();
                e1.setName("engine smoke- " + geom.getName());

                PolarizedMeshEmitterShape shape = new PolarizedMeshEmitterShape();
                //shape.setPolarity(new Vector3f(0, .73159f, -1));
                shape.setPolarity(new Vector3f(-0.02f, 1, 1.1f));
                shape.setPolarityWeight(.015f, 1);
                shape.setShape(geom.getMesh());
                e1.setShape(shape);

                //e1.setParticleType(ParticleDataImpostorMesh.class); // For particles other than the default quad impostor based particle
                e1.setMaxParticles(500);
                e1.setEmissionsPerSecond(30);
                e1.setParticlesPerEmission(5);
                e1.setDirectionType(MeshEmitterShape.DirectionType.Normal);
                e1.setBillboardMode(Emitter.BillboardMode.Camera);
                e1.setForceMinMax(.025f, .04f);
                e1.setLifeMinMax(0.6f, 2.25f);

                e1.setUseRandomEmissionPoint(true);
                e1.setParticlesFollowEmitter(false);
                // e1.setUseSequentialEmissionFace(true);
                //e1.setUseSequentialSkipPattern(true);
                //e1.setUseVelocityStretching(true);
                //e1.setVelocityStretchFactor(1.25f);

                e1.setSprite("Effects/Smoke/Smoke.png", 15, 1);
                Material mat = new Material(assetManager, "Common/MatDefs/Misc/Particle.j3md");
                mat.getAdditionalRenderState().setFaceCullMode(RenderState.FaceCullMode.Off);
                mat.getAdditionalRenderState().setBlendMode(RenderState.BlendMode.Alpha);
                e1.setMaterial(mat, "Texture", true);

                // Enabling the test mode shapes (emitter shape, particle mesh)
                //e1.setEmitterTestMode(true, true);

                // Color Influencer
                ColorInfluencer c = new ColorInfluencer();
                c.addColor(new ColorRGBA(.3f, .3f, .3f, 1f));
                c.addColor(new ColorRGBA(.2f, .2f, .2f, 1f));
                c.addColor(new ColorRGBA(.35f, .35f, .35f, 1f));
                c.setFixedDuration(0.55f);
                e1.addInfluencer(c);

                //Alpha Influencer
                AlphaInfluencer a = new AlphaInfluencer();
                a.addAlpha(1.0f, Interpolation.linear);
                a.addAlpha(0.1698f, Interpolation.linear);
                e1.addInfluencer(a);

                // Size Influencer
                SizeInfluencer s = new SizeInfluencer();
                s.addSize(new Vector3f(0.3f, 0.3f, 0.3f));
                s.addSize(new Vector3f(0.8f, 0.8f, 0.8f));
                s.setUseRandomSize(true);
                s.setRandomSizeTolerance(.25f);
                s.setFixedDuration(.6f);
                e1.addInfluencer(s);

                // Rotation Influencer
                RotationInfluencer r = new RotationInfluencer();
                r.addRotationSpeed(new Vector3f(0.0f, 0.0f, 0.0f));
                r.setUseRandomStartRotation(false, false, false);
                r.setUseRandomDirection(true);
                r.setUseRandomSpeed(true);
                e1.addInfluencer(r);

                // Gravity Influencer
                GravityInfluencer g = new GravityInfluencer();
                g.setGravity(new Vector3f(0.0f, -1, 0.0f));
                g.setMagnitude(0.75f);
                e1.addInfluencer(g);

                return e1;
        }