Variables can be set in Automation only once

I tried a script and noticed that I can set a variable only once. If I try set this variable second time nothing is changed.

Here is an example:

[code]<?xml version="1.0" encoding="UTF-8" standalone="no"?>

<variables>
	<var name="face_selector" value="0.21"/>
</variables>

<section name="NX LOD5 Export">
	<modify>
		<enable device = "nx_output_lod5"/>
		<tile number = "1"/>
	</modify>
	<build mode="tiled"/>
	<output/>
	<modify>
		<disable device = "nx_output_lod5"/>
	</modify>
</section>

<variables>
	<var name="face_selector" value="0.41"/>
</variables>

<section name="PY LOD5 Export">
	<modify>
		<enable device = "py_output_lod5"/>
		<tile number = "1"/>
	</modify>
	<build mode="tiled"/>
	<output/>
	<modify>
		<disable device = "py_output_lod5"/>
	</modify>
</section>

[/code]

“face_selector” variable controls Input Choise in Route Picker device. First changing of the variable works fine for any value. Second changing of the variable doesn’t work. Is it a bug or I do something wrong?