UDOO x86 - Can't Set Certain Arduino I/O Pins High

Hello,
I have recently noticed that I am unable to set a HIGH voltage on GPIO pins 8-15 on the Arduino on my UDOO x86 Ultra. The code I am running is:

Code:

void setup() {
  pinMode(8, OUTPUT);
  pinMode(9, OUTPUT);
  pinMode(10, OUTPUT);
  pinMode(11, OUTPUT);
  pinMode(12, OUTPUT);
  pinMode(13, OUTPUT);
  pinMode(14, OUTPUT);
  pinMode(15, OUTPUT);
}

void loop() {
  digitalWrite(8, HIGH);
  digitalWrite(9, HIGH);
  digitalWrite(10, HIGH);
  digitalWrite(11, HIGH);
  digitalWrite(12, HIGH);
  digitalWrite(13, HIGH);
  digitalWrite(14, HIGH);
  digitalWrite(15, HIGH);

  delay(3000);

  digitalWrite(8, LOW);
  digitalWrite(9, LOW);
  digitalWrite(10, LOW);
  digitalWrite(11, LOW);
  digitalWrite(12, LOW);
  digitalWrite(13, LOW);
  digitalWrite(14, LOW);
  digitalWrite(15, LOW);

 delay(3000);
}

I am still able to digitalWrite(HIGH) to pins 0-7 and A0-A5, it is only pins 8-15 which give me trouble and I am not sure why. I have never even used pins 14 and 15, so I do not think that they are broken. I also don't think that pin 13 is broken because I can see the pin 13 LED turning on and off as it should, but the pin itself is never set to 3.3V as it should be. I am measuring voltage on the pins relative to the GND pin on the Arduino and assure that it is accurate by measuring the 5V regulated pin and read 5V, so the issue is not how I am measuring. Not sure if anyone has encountered a similar problem but I have been trying to find a solution for hours with no luck.