Why POST request to Java server (jax-rs, ejb) returns bad request(400) intermittently?

Question

I am using Jax RS in a Java application hosted on SAP NEO, and I am using @EJB annotation to create a field of a @Stateful service class, and when this field is used it gives exception mentioned below: (this exception is intermittent, 90% times it works)

EjbTransactionUtil.handleSystemException: Not Found javax.ejb.NoSuchEJBException: Not Found
at org.apache.openejb.core.ivm.BaseEjbProxyHandler.convertException(BaseEjbProxyHandler.java:429)
at org.apache.openejb.core.ivm.BaseEjbProxyHandler.invoke(BaseEjbProxyHandler.java:351)
at com.sun.proxy.$Proxy130.methodCallUsingEJBField(Unknown Source)

(This is not complete stack trace)

call to method 'methodCallUsingEJBField(aTypeOfList)' is made inside method abc(String str) and method abc is called by methodXYZ(MultipartBody body)

EjbTransactionUtil.handleSystemException: The transaction has been marked rollback only because the bean encountered a non-application exception :javax.ejb.NoSuchEJBException : Not Found javax.ejb.EJBTransactionRolledbackException: The transaction has been marked rollback only because the bean encountered a non-application exception :javax.ejb.NoSuchEJBException : Not Found
at org.apache.openejb.core.ivm.BaseEjbProxyHandler.convertException(BaseEjbProxyHandler.java:420)
at org.apache.openejb.core.ivm.BaseEjbProxyHandler.invoke(BaseEjbProxyHandler.java:351)
at com.sun.proxy.$Proxy171.methodXYZ(Unknown Source)

Class definition

@Stateful
public class ServiceClasss implements InterfaceName

Field Declaration in dao

@EJB
private InterfaceName fieldName;

using the field in this way

 list = fieldName.methodCallUsingEJBField(list);

This exception is seen even if the session is active(at the time of using the application)(Was thinking about session timeout issue)

There is one another field annotated with @EJB in same dao class, it never throws exception(This EJB is of a @Stateless class)

Maven dependency

<dependency>
   <groupId>org.apache.openejb</groupId>
   <artifactId>apache-tomee</artifactId>
   <version>1.7.0</version>
   <scope>provided</scope>
</dependency>

Update: The Dao class in which i am Declaring and using that EJB is Stateless

@Stateless
public class classNaameDao{
@EJB
private InterfaceName fieldName; //the class which implements this interface is @Stateful
//some code here
list = fieldName.methodCallUsingEJBField(list);
//using the field in this statelesss class
}

Any help is appereciated.