diff --git a/platformio.ini b/platformio.ini
index 7c5b02a6..0e303f8d 100644
--- a/platformio.ini
+++ b/platformio.ini
@@ -2490,7 +2490,8 @@ build_unflags = ${env:esp32S3_8MB_M.build_unflags}   ;; use the same as "normal"
 build_flags = ${common.build_flags} ${esp32s3.build_flags} -Wno-misleading-indentation -Wno-format-truncation
   ${common_mm.build_flags_S}
   -D WLED_RELEASE_NAME=matrixportal_esp32s3
-  -DARDUINO_USB_MODE=1 -DARDUINO_USB_CDC_ON_BOOT=1 -DARDUINO_USB_MSC_ON_BOOT=0 -DARDUINO_USB_DFU_ON_BOOT=1 ;; for Hardware-CDC USB mode
+  ; Serial debug enabled  -DARDUINO_USB_MODE=1 -DARDUINO_USB_CDC_ON_BOOT=1 -DARDUINO_USB_MSC_ON_BOOT=0 -DARDUINO_USB_DFU_ON_BOOT=1 ;; for Hardware-CDC USB mode
+  -D ARDUINO_USB_CDC_ON_BOOT=0
   -D WLED_DISABLE_ADALIGHT     ;; disables serial protocols - recommended for Hardware-CDC USB (Serial RX will receive junk commands when RX pin is unconnected, unless its pulled down by resistor)
   ${common_mm.animartrix_build_flags}
   ${common_mm.build_disable_sync_interfaces}
diff --git a/tools/ESP32-Chip_info.hpp b/tools/ESP32-Chip_info.hpp
index 89316598..417ee449 100644
--- a/tools/ESP32-Chip_info.hpp
+++ b/tools/ESP32-Chip_info.hpp
@@ -543,6 +543,8 @@ void show_psram_info_part2(void)
 
 void showRealSpeed() {
   //Serial.begin(115200);
+  if (!Serial) return; // Avoid writing to unconnected USB-CDC
+
   Serial.flush();
   Serial.println(F("\n"));
   for(int aa=0; aa<65; aa++) Serial.print("="); Serial.println();
diff --git a/usermods/usermod_v2_auto_playlist/usermod_v2_auto_playlist.h b/usermods/usermod_v2_auto_playlist/usermod_v2_auto_playlist.h
index 88d62654..adb5b37e 100644
--- a/usermods/usermod_v2_auto_playlist/usermod_v2_auto_playlist.h
+++ b/usermods/usermod_v2_auto_playlist/usermod_v2_auto_playlist.h
@@ -322,6 +322,8 @@ class AutoPlaylistUsermod : public Usermod {
 
       if (bri == 0) return;
 
+      if(!functionality_enabled) return;
+
       um_data_t *um_data;
 
       if (!usermods.getUMData(&um_data, USERMOD_ID_AUDIOREACTIVE)) {
diff --git a/wled00/improv.cpp b/wled00/improv.cpp
index 646201d3..eef8ad82 100644
--- a/wled00/improv.cpp
+++ b/wled00/improv.cpp
@@ -50,6 +50,7 @@ void handleImprovPacket() {
   uint8_t rpcCommandType = 0;
   char rpcData[128];
   rpcData[0] = 0;
+  if (!Serial) return; // WLEDMM avoid reading from unconnected USB-CDC
 
   while (!timeout) {
     if (Serial.available() < 1) {
diff --git a/wled00/wled_serial.cpp b/wled00/wled_serial.cpp
index 221f21ad..9361891b 100644
--- a/wled00/wled_serial.cpp
+++ b/wled00/wled_serial.cpp
@@ -42,6 +42,7 @@ void updateBaudRate(uint32_t rate){
 // RGB LED data return as JSON array. Slow, but easy to use on the other end.
 void sendJSON(){
   if (!pinManager.isPinAllocated(hardwareTX) || pinManager.getPinOwner(hardwareTX) == PinOwner::DebugOut) {
+    if (!Serial) return; // WLEDMM avoid writing to unconnected USB-CDC
     uint16_t used = strip.getLengthTotal();
     Serial.write('[');
     for (uint16_t i=0; i<used; i++) {
@@ -55,6 +56,7 @@ void sendJSON(){
 // RGB LED data returned as bytes in TPM2 format. Faster, and slightly less easy to use on the other end.
 void sendBytes(){
   if (!pinManager.isPinAllocated(hardwareTX) || pinManager.getPinOwner(hardwareTX) == PinOwner::DebugOut) {
+    if (!Serial) return; // WLEDMM avoid writing to unconnected USB-CDC
     Serial.write(0xC9); Serial.write(0xDA);
     uint16_t used = strip.getLengthTotal();
     uint16_t len = used*3;