Plugwise Anna themostat control wrong value

[Alain]

I am writing a DzVents script to lower the thermostat setpoint on my Plugwise Anna thermostat and ran into some trouble. Because I am not fully used to scripting in DzVents, I decided to setup a simplified version in Blockly where a switch position determines what the setpoint should be.
Switch on = 15°C
Switch off = 21°C.

What is happening is, although I am setting the thermostat setpoint for the Anna, it is actually changing the setpoint for which the thermostat goes into cooling mode (in configuration settings).

Has something broken in the plugin? The value it reads seems to be OK. When I change the setpoint in the Plugwise app on my phone, it shows the corresponding value as a thermostat setpoint in Domoticz. It seems as if just the write part of the plugin is incorrect.