ContentResolver.insert returns null EVENTUALLY

I have an App which inserts data from activity and background servicer from multiply threads into 4-5 tables using custom ContentProvider.

this is AndroidManifest.xml (I don't declare android:read(write)Permission and for provider):

<application
    ...
    >
    <provider
        android:name=".content.provider.DefaultProvider"
        android:authorities="com.provider.auth"
        android:exported="false"
        android:grantUriPermissions="true"
        android:label="Default Provider"
        />
</application>

this is insert() implementation inside DefaultProvider class:

@Override
public Uri insert(Uri uri, ContentValues values) {
    UriDetail uriDetail = URI_RESOLVER.match(uri);

    if (uriDetail == null || uriDetail.isSingleItem()){
        throw new IllegalArgumentException("Unsupported URI: " + uri);
    }

    SQLiteDatabase db = dbOpenHelper.getWritableDatabase();
    long id = db.insert(uriDetail.getScheme().getName(), null, values);

    if (id != -1){
        Uri idUri;
        try {
            idUri = getUriForId(id, uri);
        } catch (SQLException e) {
            e.printStackTrace();
            throw e;
        }

        capacityManager.afterInsert(URI_RESOLVER, uriDetail, id);
        if (idUri == null){
            throw new NullPointerException(
                            "Insert into " + uriDetail.getScheme().getName() + " returned id = " + id+ " but no URI with ID was acquired!"+
                                    "\nUri: "+uri+
                                    "\nContentValues: "+values.toString()
                    );
        }
        return idUri;
    }else{
        throw new OperationApplicationException("Insert into "+uriDetail.getScheme().getName()+" returned id = "+id + "\n values: "+values.toString()));
    }

    return null;
}

UriResolver and UriDetail are helper-classes used to match URI with actual table name inside sqlite database. Also getUriForId() simply does ContentUris.withAppendedId(uri, id); and few validations. In any case - this insert() should throw Exception or return valid Uri, but not NULL. So I do regular

context.getContentResolver().insert(uri, contentValues)

receive URI and I'm happy, but rarely(!) insert() returns null without exception - it looks like DefaultProvider.insert() was not triggered at all and no record is actually inserted into db. My app works on 2.3+ devices but most of those errors I get from 4.2.2 - 4.4. Why this magic happens? Is this android issue or my mistake?