diff --git a/wled00/FX_fcn.cpp b/wled00/FX_fcn.cpp
index 34fde40058..5b923b1264 100644
--- a/wled00/FX_fcn.cpp
+++ b/wled00/FX_fcn.cpp
@@ -458,83 +458,112 @@ void Segment::handleRandomPalette() {
 // strip must be suspended (strip.suspend()) before calling this function
 // this function may call fill() to clear pixels if spacing or mapping changed (which requires setting _vWidth, _vHeight, _vLength or beginDraw())
 void Segment::setGeometry(uint16_t i1, uint16_t i2, uint8_t grp, uint8_t spc, uint16_t ofs, uint16_t i1Y, uint16_t i2Y, uint8_t m12) {
-  // return if neither bounds nor grouping have changed
-  bool boundsUnchanged = (start == i1 && stop == i2);
+  // Sanitise inputs
+  if (i2 <= i1) { // For any values, this means deactivate the segment; we check i2 before i1 for this case
+    i2 = 0;
+  } 
+
+  // If i1 is invalid, use old value
+  // Valid range is inside maxWidth, or in trailing segment range
+  if ((i1 >= Segment::maxWidth) && (i1 < Segment::maxWidth*Segment::maxHeight || i1 >= strip.getLengthTotal())) {
+    i1 = start;
+  }
+
+  // Check i2 validity
+  if (i2 > 0) {
+    // Clamp i2 to maximum length
+    if ((i1 >= Segment::maxWidth*Segment::maxHeight) && (i2 >= Segment::maxWidth*Segment::maxHeight)) {
+      // Trailing strip after 2D
+      i2 = MIN(i2,strip.getLengthTotal());
+      i1Y = 0;  // 2D Y values are not used for trailing strip
+      i2Y = 1;
+    } else if (i2 > Segment::maxWidth) {
+      i2 = Segment::maxWidth;
+    }
+  }
+
   #ifndef WLED_DISABLE_2D
-  boundsUnchanged &= (startY == i1Y && stopY == i2Y); // 2D
+  if (Segment::maxHeight>1) { // 2D
+    if (i1Y >= Segment::maxHeight) {
+      // Unlike i1 (X), Y values don't inherit old values if invalid
+      // This behaviour preserved for backwards compatibility
+      i1Y = 0;   
+    }
+    if (i2Y > Segment::maxHeight) {
+      i2Y = Segment::maxHeight;
+    } else if (i2Y < 1) {
+      i2Y = 1;
+    }
+  } else
   #endif
-  boundsUnchanged &= (grouping == grp && spacing == spc); // changing grouping and/or spacing changes virtual segment length (painting dimensions)
+  { 
+    i1Y = 0;
+    i2Y = 1;
+  }
 
-  if (stop && (spc > 0 || m12 != map1D2D)) clear();
-  if (grp) { // prevent assignment of 0
-    grouping = grp;
-    spacing = spc;
-  } else {
-    grouping = 1;
-    spacing = 0;
+  if (grp == 0) { grp = 1; spc = 0; }  // prevent assignment of 0
+  if (ofs == UINT16_MAX) ofs = offset; // keep current setting if passed illegal value
+  m12 = constrain(m12, 0, 7);
+
+  // Final safety check after all bounds adjustments
+  if ((i1 >= i2) || (i1Y >= i2Y)) { 
+    i2 = 0;  // disable segment
   }
-  if (ofs < UINT16_MAX) offset = ofs;
-  map1D2D  = constrain(m12, 0, 7);
+
+  // Inputs are ok, check if anything has changed
+  bool boundsUnchanged = (start == i1 && stop == i2)
+  #ifndef WLED_DISABLE_2D
+                       && ((Segment::maxHeight <= 1) || (startY == i1Y && stopY == i2Y))
+  #endif
+                       && (grouping == grp)
+                       && (spacing == spc)
+                       && (offset == ofs)
+                       && (m12 == map1D2D);
 
   if (boundsUnchanged) return;
 
+  DEBUG_PRINTF_P(PSTR("Segment geometry: (%d,%d),(%d,%d) -> (%d,%d),(%d,%d) [%d,%d]\n"), start, stop, startY, stopY, (int)i1, (int)i2, (int)i1Y, (int)i2Y, (int) grp, (int)spc);
+  
   unsigned oldLength = length();
 
-  DEBUGFX_PRINTF_P(PSTR("Segment geometry: %d,%d -> %d,%d [%d,%d]\n"), (int)i1, (int)i2, (int)i1Y, (int)i2Y, (int)grp, (int)spc);
   markForReset();
   stopTransition(); // we can't use transition if segment dimensions changed
   stateChanged = true;      // send UDP/WS broadcast
 
-  // apply change immediately
-  if (i2 <= i1) { //disable segment
-    #ifdef WLED_ENABLE_GIF
-    endImagePlayback(this);
-    #endif
-    deallocateData();
-    p_free(pixels);
-    pixels = nullptr;
-    stop = 0;
-    return;
-  }
-  if (i1 < Segment::maxWidth || (i1 >= Segment::maxWidth*Segment::maxHeight && i1 < strip.getLengthTotal())) start = i1; // Segment::maxWidth equals strip.getLengthTotal() for 1D
-  stop = i2 > Segment::maxWidth*Segment::maxHeight && i1 >= Segment::maxWidth*Segment::maxHeight ? MIN(i2,strip.getLengthTotal()) : constrain(i2, 1, Segment::maxWidth); // check for 2D trailing strip
-  startY = 0;
-  stopY  = 1;
-  #ifndef WLED_DISABLE_2D
-  if (Segment::maxHeight>1) { // 2D
-    if (i1Y < Segment::maxHeight) startY = i1Y;
-    stopY = constrain(i2Y, 1, Segment::maxHeight);
-  }
-  #endif
-  // safety check
-  if (start >= stop || startY >= stopY) {
-    #ifdef WLED_ENABLE_GIF
-    endImagePlayback(this);
-    #endif
-    deallocateData();
-    p_free(pixels);
-    pixels = nullptr;
-    stop = 0;
-    return;
-  }
-  // allocate FX render buffer
-  if (length() != oldLength) {
+  // apply change
+  start = i1;
+  stop = i2;
+  startY = i1Y;
+  stopY = i2Y;
+  grouping = grp;
+  spacing = spc;
+  offset = ofs;
+  map1D2D = m12;
+
+  // Cleanup check
+  auto newLength = length();
+  if ((newLength > 0) && (newLength != oldLength)) {
     // allocate render buffer (always entire segment), prefer IRAM/PSRAM. Note: impact on FPS with PSRAM buffer is low (<2% with QSPI PSRAM) on S2/S3
+    // Note we don't pass BFRALLOC_CLEAR as resetIfRequired() will initialize the buffer later
     p_free(pixels);
     pixels = static_cast<uint32_t*>(allocate_buffer(length() * sizeof(uint32_t), BFRALLOC_PREFER_PSRAM | BFRALLOC_NOBYTEACCESS));
     if (!pixels) {
       DEBUGFX_PRINTLN(F("!!! Not enough RAM for pixel buffer !!!"));
-      #ifdef WLED_ENABLE_GIF
-      endImagePlayback(this);
-      #endif
-      deallocateData();
       errorFlag = ERR_NORAM_PX;
-      stop = 0;
-      return;
+      stop = 0; // will fall through into disable check below
     }
+  }
 
+  if (length() == 0) {
+    #ifdef WLED_ENABLE_GIF
+    endImagePlayback(this);
+    #endif
+    deallocateData();
+    p_free(pixels);
+    pixels = nullptr;
+  } else {
+    refreshLightCapabilities();
   }
-  refreshLightCapabilities();
 }