diff --git a/drm/DrmConnector.cpp b/drm/DrmConnector.cpp
index 590f76f..3de4f5c 100644
--- a/drm/DrmConnector.cpp
+++ b/drm/DrmConnector.cpp
@@ -21,9 +21,11 @@
 #include <drm/drm_mode.h>
 #include <xf86drmMode.h>
 
+#include <algorithm>
 #include <array>
 #include <cerrno>
 #include <cinttypes>
+#include <cmath>
 #include <cstdint>
 #include <sstream>
 
@@ -265,6 +267,26 @@ std::string DrmConnector::GetName() const {
   return "None";
 }
 
+namespace {
+// Some EDIDs describe the same effective resolution/refresh-rate as two
+// distinct raw mode entries -- e.g. a detailed-timing "preferred" mode plus a
+// CEA-861 mode for the same nominal timing, differing only in blanking or in
+// the DRM_MODE_TYPE_PREFERRED bit. A byte-for-byte comparison (DrmMode::
+// operator==) treats these as separate modes, so both survive into the mode
+// list. That leaves which mode is "preferred" ambiguous between the kernel's
+// initial modeset and drm_hwcomposer's own selection, which is the suspected
+// cause of a mid-boot mode switch (visible as overscan until HDMI is
+// replugged) and of framework APIs like Display.getSystemPreferredDisplayMode()
+// intermittently returning null (TvSettings NPE on the Resolution screen).
+constexpr float kDuplicateModeRateEpsilonHz = 0.05F;
+
+bool IsSameEffectiveMode(const DrmMode &existing, const DrmMode &candidate) {
+  return existing.SameSize(candidate) &&
+         std::abs(existing.GetVRefresh() - candidate.GetVRefresh()) <
+             kDuplicateModeRateEpsilonHz;
+}
+}  // namespace
+
 int DrmConnector::UpdateModes() {
   std::string force_mode = Properties::GetForceMode();
   uint32_t xres = 0, yres = 0, rate = 0;
@@ -287,35 +309,43 @@ int DrmConnector::UpdateModes() {
 
   modes_.clear();
   for (int i = 0; i < connector_->count_modes; ++i) {
-    bool exists = false;
-    for (const DrmMode &mode : modes_) {
-      if (mode == connector_->modes[i]) {
-        exists = true;
-        break;
+    DrmMode m(&connector_->modes[i]);
+    ALOGV("Supported mode %dx%d@%fHz for display in connector %s",
+        m.GetRawMode().hdisplay, m.GetRawMode().vdisplay,
+        m.GetVRefresh(), GetName().c_str());
+
+    auto existing = std::find_if(modes_.begin(), modes_.end(),
+                                  [&m](const DrmMode &other) {
+                                    return IsSameEffectiveMode(other, m);
+                                  });
+    if (existing != modes_.end()) {
+      // Keep whichever duplicate carries the EDID's PREFERRED flag.
+      if ((m.GetRawMode().type & DRM_MODE_TYPE_PREFERRED) != 0 &&
+          (existing->GetRawMode().type & DRM_MODE_TYPE_PREFERRED) == 0) {
+        ALOGD("Mode %dx%d@%fHz for display in connector %s duplicated; "
+              "keeping the PREFERRED entry",
+            m.GetRawMode().hdisplay, m.GetRawMode().vdisplay,
+            m.GetVRefresh(), GetName().c_str());
+        *existing = m;
       }
+      continue;
     }
 
-    if (!exists) {
-      DrmMode m(&connector_->modes[i]);
-      ALOGV("Supported mode %dx%d@%fHz for display in connector %s",
-          m.GetRawMode().hdisplay, m.GetRawMode().vdisplay,
-          m.GetVRefresh(), GetName().c_str());
-      if (xres && yres) {
-        if (!rate && m.GetRawMode().hdisplay == xres
-            && m.GetRawMode().vdisplay == yres) {
-          rate = m.GetVRefresh();
-        }
-        if (m.GetRawMode().hdisplay != xres
-            || m.GetRawMode().vdisplay != yres
-            || m.GetVRefresh() != rate) {
-          continue;
-        }
+    if (xres && yres) {
+      if (!rate && m.GetRawMode().hdisplay == xres
+          && m.GetRawMode().vdisplay == yres) {
+        rate = m.GetVRefresh();
+      }
+      if (m.GetRawMode().hdisplay != xres
+          || m.GetRawMode().vdisplay != yres
+          || m.GetVRefresh() != rate) {
+        continue;
       }
-      ALOGD("Add mode %dx%d@%fHz for display in connector %s",
-          m.GetRawMode().hdisplay, m.GetRawMode().vdisplay,
-          m.GetVRefresh(), GetName().c_str());
-      modes_.emplace_back(m);
     }
+    ALOGD("Add mode %dx%d@%fHz for display in connector %s",
+        m.GetRawMode().hdisplay, m.GetRawMode().vdisplay,
+        m.GetVRefresh(), GetName().c_str());
+    modes_.emplace_back(m);
   }
 
   return 0;