Unwritable property defined in extension package

I have a ThingTemplate defined in a Java ext pkg, and it has lots of properties defined as well. One of those properties is "Phone", as defined by

public static final String PROPERTY_PHONE = "PhoneNumber";

I define this property like this

@ThingworxPropertyDefinition(name= Constants.PROPERTY_PHONE, description="Phone Number", baseType="STRING", aspects={"isPersistent:true","isReadOnly:false"}),

I also have code to set this property.

thing.setPropertyValue(Constants.PROPERTY_PHONE, new StringPrimitive(newValue));

This is the pattern I have for a bunch of properties, a constant defining the property name, used by the ThingworxPropertyDefinition and then the setter (and getter).

This works fine, except for this single damn property called "Phone". When I go to set this I get an empty exception with no details. In fact I cannot find any way to set this property, via Composer, REST, etc. It is unsettable.

Literally, if I change the name in the constants file from "Phone" to "Phone2", recompile, re-import, bounce tomcat, everything works. But changing back to "phone" it busts.

I have no idea how this is happening or why, and I am going to play around with defining this property in XML rather than in Java, but I am really grasping at straws here..

Any ideas out there?