Probelms with Adafruit_MQTT_Publish::publish

[nelisse]

The Adafruit_MQTT_Publish::publish(int32_t) and Adafruit_MQTT_Publish::publish(uint32_t i) already rollover after 32768 (because they use the itoa function).
The Adafruit_MQTT_Publish::publish(double f.... could potentially have a buffer problem (because of unsuffiient room for a terminating zero).

I think this will fix it:

bool Adafruit_MQTT_Publish::publish(int32_t i) {
  char payload[12];  // Need to technically hold int32 max: 10 digits, minus sign and terminating zero.
  ltoa(i, payload, 10); // // Changed itoa to ltoa, int32_t => long
  return mqtt->publish(topic, payload, qos);
}

bool Adafruit_MQTT_Publish::publish(double f, uint8_t precision) {
  char payload[41];  // Need to technically hold float max, 39 digits, minus sign and terminating zero.
  dtostrf(f, 0, precision, payload);
  return mqtt->publish(topic, payload, qos);
}

bool Adafruit_MQTT_Publish::publish(uint32_t i) {
  char payload[11];  // Need to technically hold uint32 max: 10 digits and terminating zero.
  ultoa(i, payload, 10); // Changed itoa to ultoa, uint32_t => unsigned long
  return mqtt->publish(topic, payload, qos);
}

[ladyada]

changed payload to [41]!