Strange error while reading settings for datafield

Dear fellows;

Sometimes I get strange errors via ERA for my datafields which I cannot understand or do something against. 
Here is one of them:

Line 635 in View is reading the variable rpmSwap from settings:

        isColored = Application.Properties.getValue("_isColored");
        isEnvelope = Application.Properties.getValue("_isEnvelope");
        isPower = Application.Properties.getValue("_isPower");
        caloriesToggle = Application.Properties.getValue("_caloriesToggle");
        rpmSwap = Application.Properties.getValue("_rpmSwap");  // LINE 635 OF ERROR
        isLaps = Application.Properties.getValue("_isLaps");
        isPozone7 = Application.Properties.getValue("_isPozone7");
        cadMax = Application.Properties.getValue("_cadMax");
        hrMax = Application.Properties.getValue("_hrMax");
        gradDigits = Application.Properties.getValue("_gradDigits");

_rpmSwap in settings is Boolean - it can only be true or false - and it is present in settings.XML

		<property id="_isPower" type="boolean">true</property>
		<property id="_caloriesToggle" type="boolean">true</property>
		<property id="_rpmSwap" type="boolean">false</property>
		<property id="_isLaps" type="boolean">true</property>
		<property id="_isPozone7" type="boolean">false</property>

As I said before - such errors happen from time to time - not regularly.
( I myself use this datafield, too - and I never experienced that error)

I think - I have to live with it - or?