Not all classes with different group tag are getting executed from testNG.xml

I have 15 classes in my project. Each class contains multiple @Test and each test may have either of 1-Smoke 2-Regression 3-("Smoke","Regression") group. When i am trying to execute include name="Regression" group, some(5) of all 15 classes are getting executed.Also in executed classes all @Test which contains"Regression" are not getting executed.If i comment classes which are getting executed everytime than other classes (which are not getting executed)also gets execute.

I tried with Pakage rather then classes, but facing same issue. I also checked spelling and everything looks fine for me

Below is my XML-

        <groups>    
            <run>   
                 <include name="Regression" />  
            </run>  
        </groups>   

<classes >
            <class name="com.lrm.qa.testcases.AccidentPageTest"/>
            <class name="com.lrm.qa.testcases.ClaimInQueueTest"/>
            <class name="com.lrm.qa.testcases.CustomQuestionsAcostaPageTest"/>
            <class name="com.lrm.qa.testcases.EmployeePageTest"/>
            <class name="com.lrm.qa.testcases.EmployerPageTest"/>
            <class name="com.lrm.qa.testcases.GetStartedPageTest"/>
            <class name="com.lrm.qa.testcases.HomePageTest"/>
            <class name="com.lrm.qa.testcases.LoginPageTest"/>
            <class name="com.lrm.qa.testcases.LogOffPageTest"/>
            <class name="com.lrm.qa.testcases.LossReportGenerationPageTest"/>
            <class name="com.lrm.qa.testcases.LossReportSelectionPageTest"/>
            <class name="com.lrm.qa.testcases.SavedReportPageTest"/>
            <class name="com.lrm.qa.testcases.SearchPageTest"/>
            <class name="com.lrm.qa.testcases.StateSpecificQuestionsAZPageTest"/>
            <class name="com.lrm.qa.testcases.WrapUpPageTest"/>

</classes>

I am expecting when i execute TestNG.xml, all the @Test which have Regression tag will execute.