Adax neo compact wifi heater: select watt (power) in android app is not saving the result

Just a strange phenomenon I encounterd in te Adax app.

it is posible to change the heaters power (Select Watt) in the webapp (see picture). so there is no real problem.

But I cannot change this setting in the android app. in the android app the setting will not save the new entry. Tried it on two phones.