The resistance is gain calibrated in the factory but is not offset calibrated, so the -1.1Ω you’re seeing makes sense. Zeroing this out before making small resistance measurements is the best way around this.
The temperature is actually not calibrated at the factory, so sometimes a unit with a temperature offset slips through. I can arrange an exchange if that’s a deal-breaker for you, but if that doesn’t matter so much to you then you can rest assured the offset doesn’t affect any other readings.
Sorry for the delay on this, best