FitContributor Unexpected type error on Edge 1040

Hi, I am getting an Unexpected type error in runtime when I try to run my complex datafiled on the Edge1040 simulator. Other devices run fine in the sim. 

SDK: 4.1.4

Here is the code, the problem is with this line: mFitBGField.setData(0.0);

class dexDFView extends WatchUi.DataField {

    hidden var mValue;
    
    var mMessage;
	var mFitBGField = null;	

    function initialize() {
        DataField.initialize();
        mValue = 0; 
        mMessage = "";
                
        mFitBGField = createField(
       					"Glucose", 
       					0, 
       					FitContributor.DATA_TYPE_FLOAT, 
       					{:mesgType=>FitContributor.MESG_TYPE_RECORD, :units=>"mmol or mg/dl" }
       	);
        
        mFitBGField.setData(0.0);
    }

 I can't see any obvious isues with the code, and it runs fine on other Edge devices 

Run-time error:

Error: Unexpected Type Error
Details: Failed invoking <symbol>