Megamenu configuration is saved but not shown in frontend

Hi
I'm running an internal KB for my team based on Joomla!:
Joomla! Version Joomla! 3.3.6 Stable [ Ember ] 01-October-2014 02:00 GMT
Joomla! Platform Version Joomla Platform 13.1.0 Stable [ Curiosity ] 24-Apr-2013 00:00 GMT
Template: T3 Bs3 Blank ver 2.1.6
T3 Framework ver 2.4.0

I have an issue with the Megamenu configuraiton.
Yesterday I configured the Megamenu as Following:


And it was working until today when I added more entries in the next sub-menu. Now the configuration is ok as Megamenu still shows the proper config but the frontend view is like this:


Can anyone tell me what is the cause?
I had this issue before but then i just recreated the menu in a new one and selected that as the Megamenu.

Update:

I think I was able to identify the point when the configuration goes to hell. When configuring new entries in them menu Manager after adding an entry or renaming it the menu starts only to show modules in the submenu an nothing else and also stops being updated from the level of Megamenu.