Test show that the waterpump works, but water is dispensed only once a minute in high mode. This is barely enough. So I'd suspect that Xiaomi prolonged the interval in some firmware update.
Same here for Mi Robot Vacuum-Mop 2 Ultra. I have two devices of this type and both stopped mopping properly at the same time, i.e. they hardly dispense any water anymore. Firmware is 4.3.3_1167 (latest)