Jetty 9.4.4 or above causes Servlet not Found 404 Error - servlets

Question

When I upgrade to Jetty 9.4.4 or greater I get a new error 404 on some of my Servlets. All is fine till this specific version. Has anyone encountered this problem, too? Luckily I am able to pin the version to 9.4.3, but I would like to resolve this issue if possible.
I use Maven and Netbeans to build the JEE 7.0 Application. It is deployed as WAR file on a Server running Jetty in a Docker container.
The Servlet is defined as follows:
import javax.servlet.annotation.WebServlet;
import javax.servlet.http.HttpServletRequest;
#WebServlet(urlPatterns = "/WebNumberCheckServlet")
public class WebNumberCheckServlet extends AbstractWebBaseServlet {
where AbstractWebBaseServlet is:
import javax.servlet.ServletException;
import javax.servlet.http.HttpServlet;
import javax.servlet.http.HttpServletRequest;
import javax.servlet.http.HttpServletResponse;
public abstract class AbstractWebBaseServlet extends HttpServlet {
web.xml is only used for realm config:
<?xml version="1.0" encoding="UTF-8"?>
<web-app version="2.5" xmlns="http://java.sun.com/xml/ns/javaee"
xmlns:xsi="http://www.w3.org/2001/XMLSchema-instance"
xsi:schemaLocation="http://java.sun.com/xml/ns/javaee
http://java.sun.com/xml/ns/javaee/web-app_2_5.xsd">
<listener>
<listener-class>de.lindawerner.pimp.pimpserver.ContextListener</listener-class>
</listener>
<session-config>
<session-timeout>
30
</session-timeout>
</session-config>
<welcome-file-list>
<welcome-file>index.jsp</welcome-file>
</welcome-file-list>
<security-constraint>
<display-name>Constraint1</display-name>
<web-resource-collection>
<web-resource-name>Protected</web-resource-name>
<description/>
<url-pattern>/stats.jsp</url-pattern>
</web-resource-collection>
<auth-constraint>
<description/>
<role-name>admin</role-name>
</auth-constraint>
</security-constraint>
<login-config>
<auth-method>BASIC</auth-method>
<realm-name>AppOnlineServerRealm</realm-name>
</login-config>
<security-role>
<description>Administrator</description>
<role-name>admin</role-name>
</security-role>