Crosswalk version issue

I recently noticed my app not working for certain android versions (4.4.4). The adb logcat seemed to indicate an error in crosswalk, so I reinstalled it. After comparing this with one of my working apps, I noticed in config.xml, it added the line

<preference name="xwalkVersion" value="20+" />

In the working app this version was set to 19, so I changed the line to

<preference name="xwalkVersion" value="19+" />

solved the problem …

Does any one know what is happening here?