Smart ph, EC/TDS combined monitor, incomplete product

The pH probe does not measure 100% accurately (after calibration to ph 7 it shows 4.3 at ph 4). EC measures correctly. The warranty only covers the measuring device, not the probe, unfortunately we do not have a replacement.

Pocket pH and EC monitor Milwaukee SM802 with external probe MA850 (combined EC and pH), manual 1-point calibration for EC and pH 4 or 7, power supply - 9V battery, automatic temperature compensation, resolution 0.1 (pH) and 0.01 (EC), calibration solutions, dimensions 185x82x45mm.