Sub menu items no appearing in mobile version

Hy, my site www.montessorinet.it (Joomla 2.5.11, template ja_purity_ii, MobileJoomla 1.2.5.1) has a main menu where some items are defined as "text separator" type because they don't link to article but show only sub menu voices. It works fine on desktop version but not in mobile version where these menu voices are "mute" (only text string without submenu items). Some suggestion how can I solve this problem? Thanks for attention.