Hi James,
Yes using the zero button allows me to measure 1 Ohm reasonably accurately but it only works with the range locked. On auto range the zero value disappears when I disconnect the probes as it switches to the high range. When I attach the 1 Ohm resistor it goes back to the low range, the zero value re-appears, but it doesn’t get subtracted. So I think there is a small bug there.

Also it is a bit odd that with the probes open circuit it shows something like 1.5K on the low range. When auto ranging it shows out of range as I would expect.