I remember, I had similar problems in the past in my m4a-project.
I have fixed it, by adding I18N.West-Reference to the project, manually.
To avoid it from linking, you can add I18N.West assembly to the exclude from linking-option in the project properties.
you can also generate some pseudo-code, that runs on project-start, to avoid linking f.e.:
var cp1252 = new I18N.West.CP1252();
This should not embedded in a method, that will never called in you project, because, then, the linker will remove it. I have this code in OnCreate in my start-activity.
Maybe there are other/better solutions. But this helped me to fix it.