diff --git a/dashboard/js/app.js b/dashboard/js/app.js
index 69beed8..8315900 100644
--- a/dashboard/js/app.js
+++ b/dashboard/js/app.js
@@ -2286,13 +2286,7 @@
             // Fallback without Layers module
             var btn = document.getElementById('fresnel-toggle-btn');
             var isActive = btn && btn.classList.contains('active');
-            if (isActive) {
-                Viz3D.toggleFresnelZones(false);
-                if (btn) btn.classList.remove('active');
-            } else {
-                Viz3D.toggleFresnelZones(true);
-                if (btn) btn.classList.add('active');
-            }
+            toggleFresnelDebugOverlay(!isActive);
         }
     };
 
@@ -2307,11 +2301,6 @@
     window.toggleFresnelDebugOverlay = function(visible) {
         state.fresnelDebugVisible = visible;
 
-        // Sync Viz3D Fresnel zones with debug overlay state
-        if (window.Viz3D && Viz3D.toggleFresnelZones) {
-            Viz3D.toggleFresnelZones(visible);
-        }
-
         // Sync toolbar button
         var btn = document.getElementById('fresnel-toggle-btn');
         if (btn) {
diff --git a/dashboard/js/fresnel.js b/dashboard/js/fresnel.js
index bfe17e7..f1f8fe5 100644
--- a/dashboard/js/fresnel.js
+++ b/dashboard/js/fresnel.js
@@ -233,22 +233,16 @@
     function removeFresnelEllipsoid(ellipsoid) {
         if (!ellipsoid) return;
 
-        if (ellipsoid.wireframe && _scene) {
-            _scene.remove(ellipsoid.wireframe);
-            ellipsoid.wireframe.geometry.dispose();
-            if (ellipsoid.wireframe.material) {
-                ellipsoid.wireframe.material.dispose();
-            }
+        if (ellipsoid.wireframe) {
+            if (_scene) _scene.remove(ellipsoid.wireframe);
+            if (ellipsoid.wireframe.geometry) ellipsoid.wireframe.geometry.dispose();
+            if (ellipsoid.wireframe.material) ellipsoid.wireframe.material.dispose();
         }
 
-        if (ellipsoid.fill && _scene) {
-            _scene.remove(ellipsoid.fill);
-            if (ellipsoid.fill.geometry) {
-                ellipsoid.fill.geometry.dispose();
-            }
-            if (ellipsoid.fill.material) {
-                ellipsoid.fill.material.dispose();
-            }
+        if (ellipsoid.fill) {
+            if (_scene) _scene.remove(ellipsoid.fill);
+            if (ellipsoid.fill.geometry) ellipsoid.fill.geometry.dispose();
+            if (ellipsoid.fill.material) ellipsoid.fill.material.dispose();
         }
     }
 
diff --git a/dashboard/js/fresnel.test.js b/dashboard/js/fresnel.test.js
index 43ce1e3..7ceeefa 100644
--- a/dashboard/js/fresnel.test.js
+++ b/dashboard/js/fresnel.test.js
@@ -30,6 +30,8 @@ describe('Fresnel Module', function() {
                     this.position = { copy: function() {} };
                     this.quaternion = { copy: function() {} };
                     this.userData = {};
+                    this.geometry = { dispose: function() {} };
+                    this.material = { dispose: function() {} };
                 },
                 MeshBasicMaterial: function() {},
                 Mesh: function() {
@@ -37,6 +39,8 @@ describe('Fresnel Module', function() {
                     this.position = { copy: function() {} };
                     this.quaternion = { copy: function() {} };
                     this.userData = {};
+                    this.geometry = { dispose: function() {} };
+                    this.material = { dispose: function() {} };
                 },
                 DoubleSide: 2
             };
diff --git a/dashboard/js/viz3d.js b/dashboard/js/viz3d.js
index d1ebae1..3ad6cb5 100644
--- a/dashboard/js/viz3d.js
+++ b/dashboard/js/viz3d.js
@@ -2914,9 +2914,9 @@ const Viz3D = (function () {
         // Ellipsoid semi-axes calculation
         // For a prolate spheroid with foci at tx and rx:
         // Semi-major axis (a) = (d + deltaL) / 2
-        // Semi-minor axis (b) = sqrt(deltaL * (d + deltaL)) / 2
+        // Semi-minor axis (b) = sqrt(deltaL * (2*d + deltaL)) / 2
         const a = (d + deltaL) / 2;
-        const b = Math.sqrt(deltaL * (d + deltaL)) / 2;
+        const b = Math.sqrt(Math.max(0, deltaL * (2 * d + deltaL))) / 2;
 
         // Center of ellipsoid (midpoint between TX and RX)
         const center = new THREE.Vector3().addVectors(tx, rx).multiplyScalar(0.5);