maybe, this issue didn't exist after all

manual_control/manual_control.ino

@@ -41,7 +41,6 @@ void setup() { //initial setup and reset
     pins[i]=LOW;
   } // setup serial connection
   Serial.begin(115200);
-  delay(100); //Printing the welcome message immediately may cause the serial communication to not function properly.
   Serial.print(color_null+"-=[ Arduino Serial Manual Pin Control ]=-\n\r");
 }