Sub menus not working at smaller viewports

[artguycreative]

Seems to work at 1024 (though inconsistent in that at times all of the sub menus show on Menu click.) Smaller viewports inconsistently show or hide all menus on Menu click. If hidden, Menu click only reveals main menus. At full size, the menus work, though somewhat erratically.

[artguycreative]

http://www.artguycreative.com/matthaiSite/