diff --git a/tidy3d/plugins/mode/solver.py b/tidy3d/plugins/mode/solver.py
index 5887b5e840..7230974861 100644
--- a/tidy3d/plugins/mode/solver.py
+++ b/tidy3d/plugins/mode/solver.py
@@ -90,7 +90,7 @@ def compute_modes(
         angle_phi = mode_spec.angle_phi
         omega = 2 * np.pi * freq
         k0 = omega / C_0
-        enable_incidence_matrices = split_curl_scaling is not None or mu_cross is not None
+        enable_incidence_matrices = False  # Experimental feature, always off for now
 
         eps_formated = cls.format_medium_data(eps_cross)
         eps_xx, eps_xy, eps_xz, eps_yx, eps_yy, eps_yz, eps_zx, eps_zy, eps_zz = eps_formated
@@ -331,6 +331,7 @@ def conductivity_model_for_pec(eps, threshold=0.9 * pec_val):
             return eps
 
         eps_tensor = conductivity_model_for_pec(eps_tensor)
+        mu_tensor = conductivity_model_for_pec(mu_tensor)
 
         # Determine if ``eps`` and ``mu`` are diagonal or tensorial
         off_diagonals = (np.ones((3, 3)) - np.eye(3)).astype(bool)