Teensy 3.5 I2C stops working after a while

[sstaub]

I made a simple sketch for using the I2C IO Expander MCP23017 with a teensy 3.5 board.
Using Teensyduino v1.40 with Arduino IDE 1.8.5
The pullup resistors (4.7k) are OK.
After a short while (between 5s up to 2min) the expander stops working.

#include <Wire.h>
#include "Adafruit_MCP23017.h"

Adafruit_MCP23017 mcp;
  
void setup() {  
  mcp.begin();      // use default address 0
  mcp.pinMode(6, OUTPUT);
  mcp.pinMode(7, OUTPUT);
}

void loop() {
  delay(500);
  mcp.digitalWrite(6, HIGH);
  mcp.digitalWrite(7, LOW);
  delay(500);
  mcp.digitalWrite(6, LOW);
  mcp.digitalWrite(7, HIGH); 
}

What's wrong?

 

[sstaub]

It seems that it is a problem with the chip. I have the same problem on Arduino UNO.
Sorry.

 

[Theremingenieur]

Isn't there an improved and optimized wire library, especially for the Teensy 3.x processors?