Google playstore gson serialize difers from gson serialize from local install

Question

I have this class

public class _CtV3 {
    private long   _ct_id;
    private String _ct_eml;
    private int    _ct_lst;
    private int    _ct_til;
    private String _ct_gid;
    private int    _ct_ntr;
    private int    _ct_nle;
    private int    _ct_nlm;
    private String _ct_uui;

    public _CtV3(long ct_id, String ct_eml, int ct_lst, int ct_til, String ct_gid, int ct_ntr, int ct_nle, int ct_nlm, String ct_uui) {
        this._ct_id  = ct_id;
        this._ct_eml = ct_eml;
        this._ct_lst = ct_lst;
        this._ct_til = ct_til;
        this._ct_gid = ct_gid;
        this._ct_ntr = ct_ntr;
        this._ct_nle = ct_nle;
        this._ct_nlm = ct_nlm;
        this._ct_uui = ct_uui;
    }
    ...
}

which at some point is serialized with Gson with...

 String uuid = UUID.randomUUID().toString();
 ctV3 = new _CtV3(0, "", 0, 0, "", 0, -1, 0, uuid);

 GsonBuilder builder = new GsonBuilder();
 Gson gson = builder.create();
 String dec = gson.toJson(ctV3);

 Log.d(TAG, dec);

Now the problem. If I install on an android phone directly from Android Studio everything works fine and Log returns

{"_ct_eml":"","_ct_gid":"","_ct_id":0,"_ct_lst":0,"_ct_nle":-1,"_ct_nlm":0,"_ct_ntr":0,"_ct_til":0,"_ct_uui":"f0438604-a22b-44d3-bb4b-9303a828b0f9"}

If I install on the same phone from Google PlayStore the same Log returns

{"a":0,"b":"","c":0,"d":0,"e":0,"f":-1,"g":0,"h":"19ff09be-07d1-411d-a625-bcf4b574abec"}

This issue came up last month as my last upgrade took place in early September.