What really determines the language of ciq fitcontribution field

Hi,

I have an app,some of the code is

<fitContributions>

<fitField id="1" displayInActivitySummary="true" sortOrder="1" precision="0"
dataLabel="@Strings.jtl" unitLabel="@Strings.jtu"/>

</fitContributions>
totalTime = mSession.createField("totalTimeField", 1, FitContributor.DATA_TYPE_STRING, {:mesgType => FitContributor.MESG_TYPE_SESSION,:count=>10});
I have several string.xml s under resources-xxx to do i18n.
However, I find the field name on my Chinese users GCM some are Chinese while some are English,in which case I really doubt what determines the localization?Is it another ciq bug?
I used to thought the culprit perhaps is which resources-xxx is used, on some occasion, resources(default is eng) was used while sometimes resources-zhs was used. An idea appeared in my mind was the ciq had to fallback to the default resources due to lack of chs(after all I saw it in the era report viewer).
Util I  noticed that 
Travis

You don't need to change anything. Internally, the compiler and runtime system use cht and chs for Traditional and Simplified Chinese language codes. We map zht to cht and zhs to chs internally.

This thought gone away.
So do you have any idea?
Here are some screenshots for this issue