"climate / fan speed / decrease" --especially when the fan comes on at full blast--is NEVER understood by the voice system. If it hears anything, it thinks that "decrease" is "degrees," and tries to change the temperature.
First of all, have the fan set so that it does not come on at full blast, every time. (Ideally, let the user program the default, or have it default to whatever setting it was last left on.)
Secondly, use some other word than "decrease" for functions within "climate," as the confusion between "decrease" and "degrees" can only be made, reliably, with practice...and when the fan is ALREADY at one of its lowest two settings (which means you don't need to decrease it further, at that point).
First of all, have the fan set so that it does not come on at full blast, every time. (Ideally, let the user program the default, or have it default to whatever setting it was last left on.)
Secondly, use some other word than "decrease" for functions within "climate," as the confusion between "decrease" and "degrees" can only be made, reliably, with practice...and when the fan is ALREADY at one of its lowest two settings (which means you don't need to decrease it further, at that point).