Buffered PWM not working for values of 0 or 255 - ATTiny3227 and 3217

[CreativeRobotics]

When selecting buffered PWM on PB0-2 or PB3-5 (any of the buffered options in the menu) the PWM cannot be set to 0% or 100%. If you are anywhere in between and try to set the PWM to either 0 or 255 it will not change the PWM value at all.

Using digitalWrite to set the pin to on or off doesn't work either.

Unbuffered PWM appears to work fine.

I have tested this on a 3227 and a 3217 (Curiosity Nano board) running at 8Mhz and with all other MegaTinyCore options at their defaults.

I used the code below, and an oscilloscope to monitor the output.

int pwmPin = PIN_PB0;
void setup() {
  // put your setup code here, to run once:
  pinMode(pwmPin, OUTPUT);
}

void loop() {
  // put your main code here, to run repeatedly:
  analogWrite(pwmPin, 128);
  delay(1000);
  
  analogWrite(pwmPin, 254);
  delay(1000);

  analogWrite(pwmPin, 255);
  delay(1000);
  
  digitalWrite(pwmPin, 1);
  delay(1000);


  analogWrite(pwmPin, 128);
  delay(1000);
  
  analogWrite(pwmPin, 1);
  delay(1000);
  
 
  analogWrite(pwmPin, 0);
  delay(1000);

  digitalWrite(pwmPin, 0);
  delay(1000);

}