Water Level Sensor - always > 40%

Hey hey,

by now I have two Grove Water Level Sensors, both showing the same behaviour. Whenever I turn them on, they start of with a base level of 40% - when I put them in water the level rises, but it never goes lower than 40%.

The code is exactly the code from the linked example page. However, it still does not go lower.

When looking at the logs for the high and the low values, there is a peculiarity … the low value never changes.

[18:48:43][D][custom:033]: low 8 sections value =
[18:48:43][D][custom:035]: high 12 sections value =

Does anyone have a clue when this will happen? If the cable would be wrong, the I2C bus protocol would probably show no data at all, correct?
I also tried with both 3V and 5V, just no changes. It is also not the sensor, as I now tried two of them.

Anyone having an idea?