Domoticz

Trying to control ventilation via a dimmer (device WTW) based on CO2 values (device MS1 CO2). The blockly script gets triggered every minute according to log, but nothing seems to be executed. Global user variables (WTWspeed & WTWtarget) are not updated, nothing is written to log, devices doesn't get set.

EventSystem is enabled, so is dzVents.
Manual operation of WTW dimmer via slider or event works fine.

Am I overlooking something that causes the instructions of the script not to work?

Simple test script to write CO2 value directly to log shows that it's empty.
All other values of the sensor do come throug. See images.