If errors are skewed in one direction there would likely have to be a factor forcing it, like sampling and response bias. That's always possible, though again

If errors are skewed in one direction there would likely have to be a factor forcing it, like sampling and response bias. That's always possible, though again I question the validity of the measure and results if its getting consistently skewed results. Either the methodology is faulty or the results simply can't be trusted because they can't reliably get good data.