PrimeFaces commandButton is not working - primefaces

Question

I know this is a very common issue which happens for a variety of reasons, but although I have searched about it a lot, I didn't manage to find a solution for my case.
My primefaces commandButton is inside an h:form and is declared as follows:
<p:commandButton action="#{userGroupBean.createOrUpdateItemAction}"
value="#{userGroupBean.actionCreateOrUpdateLabel}"
icon="iconDisk"
update="#form"
oncomplete="window.scrollTo(0,0);" />
My UserGroupBean is ViewScoped.
This button when clicked is supposed to create a userGroup and show a "Successful creation" message. Instead of doing this it just shows "Please wait" loader for a second and then does nothing. There are no errors in the log and through remote debugging I confirmed that it doesn't enter the action method.
The weird thing is that when I run the same code in a local Tomcat installation it runs successfully. Also, on the remote server this application is deployed, this used to work just fine. All happened suddenly, and I have a lot of commandButtons like this one, across my application which still work great. Something seems to go wrong just with this particular page .
I use PrimeFaces 3.1 version, I dont know what other information is usefull to provide.
Any help/ideas is/are appreciated.
EDIT
This is userGroup.xhtml (the page whose buttons do not work) code:
<ui:composition
xmlns="http://www.w3.org/1999/xhtml"
xmlns:h="http://java.sun.com/jsf/html"
xmlns:ui="http://java.sun.com/jsf/facelets"
xmlns:p="http://primefaces.org/ui"
xmlns:c="http://java.sun.com/jsp/jstl/core"
xmlns:f="http://java.sun.com/jsf/core"
xmlns:fn="http://java.sun.com/jsp/jstl/functions"
xmlns:comps="http://java.sun.com/jsf/composite/components"
template="/WEB-INF/templates/userGroup/edit.xhtml">
<f:metadata>
<f:event type="preRenderView" listener="#{userGroupBean.initUserGroupUsersList}" />
</f:metadata>
<ui:define name="title">
User Group
</ui:define>
<ui:define name="centerUnit">
<h:form>
<h:panelGrid columns="3" styleClass="ui-messages-info ui-corner-all" rendered="#{not empty flash.messages_info}">
<span class="ui-message-info-icon"></span>
#{flash.messages_info}
</h:panelGrid>
<p:messages showDetail="true" globalOnly="true" />
<p:panel header="Settings">
<h:panelGrid columns="3" cellpadding="5">
<h:outputLabel for="title" value="User Group Title:" />
<p:inputText id="title" value="#{userGroupBean.userGroup.title}" />
<p:message for="title" />
</h:panelGrid>
</p:panel>
<p:panel header="Members">
<p:pickList value="#{userGroupBean.usersGroupUsersList}" var="user"
iconOnly="true"
converter="userConverter"
itemLabel="#{user.username}" itemValue="#{user}">
<f:facet name="sourceCaption">Available</f:facet>
<f:facet name="targetCaption">Participating</f:facet>
<p:column style="width:25%">
<p:graphicImage value="#{facesContext.externalContext.request.contextPath}/../file?thumbnail=&downloadPath=#{user.contactDetails.picture.downloadPath}" width="40" height="40" />
</p:column>
<p:column style="width:25%">
<h:outputText value="#{user.username}" />
</p:column>
<p:column style="width: 50%">
<h:outputText value="#{user.contactDetails.lastName} #{user.contactDetails.firstName}"/>
</p:column>
</p:pickList>
</p:panel>
<p:commandButton
action="#{userGroupBean.createOrUpdateItemAction}"
value="#{userGroupBean.actionCreateOrUpdateLabel}"
icon="iconDisk"
update="#form"
oncomplete="window.scrollTo(0,0);" />
<p:separator />
<p:outputPanel style="text-align:right" layout="block" rendered="#{!userGroupBean.userGroup.isNew() and userGroupBean.hasUserModifyUserGroupAuthority()}">
<h:panelGroup>
<p:commandButton value="Delete" title="Do you want to delete this user group?"
action="#{userGroupBean.deleteItemAction}"
update="#form"
icon="iconDelete" />
<p:commandButton value="Leave user group" title="I want to leave this user group"
action="#{userGroupBean.userInSessionLeavesUserGroupAction}"
update="#form"
icon="iconUserGo"/>
</h:panelGroup>
</p:outputPanel>
</h:form>
</ui:define>
The UserGroupBean.java:
#Controller("userGroupBean")
#Scope(value = "view")
public class UserGroupBean extends GenericBean<UserGroup> {
private static final long serialVersionUID = 1L;
final Log logger = LogFactory.getLog(getClass());
#Autowired
private SessionServiceImpl sessionService;
#Autowired
protected UserGroupService userGroupService;
#Autowired
protected UserService userService;
#Override
public String getPageCreateOrUpdate() { return "userGroup.xhtml"; }
#Override
public String getPageList() { return "../../my/userGroups.xhtml"; }
/** Wrapper method which calls getItem() */
public UserGroup getUserGroup() { return getItem(); }
/** Wrapper method which calls setItem() */
public void setUserGroup(UserGroup UserGroup) { setItem(UserGroup); }
protected UserGroup findItemById(Integer userGroupId) {
return userGroupService.findUserGroupById(userGroupId);
}
#Override
protected void resolveCreateRequest(HttpServletRequest req) {
logger.debug("UserGroupBean::resolveCreateRequest()");
setItem( userGroupService.initializeUserGroup("") );
}
#Override
protected String createItem() {
try {
if(!isValidUsersSelection(new ArrayList<User>(usersGroupUsersList.getTarget())))
return null;
List<Integer> userIds = new ArrayList<Integer>();
for(User user: usersGroupUsersList.getTarget())
userIds.add(user.getId());
userGroupService.saveUserGroup(getUserGroup(), userIds);
helperFacesContext.addInfoMessageToFlash("User Group successfully created.");
return getPageCreateOrUpdate()+"?action=update&id="+getItem().getId()+"&faces-redirect=true";
}
catch (Exception e) {
JsfUtils.error("There was an error", e.getMessage());
return null;
}
}
.....
}
And finally the UservConverter.java
#FacesConverter(value = "userConverter")
public class UserConverter extends GenericConverter {
final Log logger = LogFactory.getLog(getClass());
private UserDAO getUserDAO(FacesContext facesContext) {
// #Autowired gives null
return (UserDAO) FacesContextUtils.getWebApplicationContext(facesContext).getBean("userDAO");
}
/**
* converts the String representation of the key back to the Object
*/
#Override
public Object getAsObject(FacesContext context, UIComponent component,
String value) throws ConverterException {
logger.info("UserConverter::getAsObject("+value+")");
Integer userId = Integer.valueOf(value);
try {
return getUserDAO(context).findById(userId);
} catch(Exception e) {
throw new ConverterException(handleException(context,e.getMessage()));
}
}
NEW CLUE: When I restart the server and only after that, when I access this page and manage to create a user group before userGroup.xhtml is fully loaded, the user group is created just fine. If I restart the server and wait till the page is loaded and then create a user group again nothing happens. This problem will drive me crazy at the end.