Drop-down menus (from Main) doing funny things

On my landing page, the menu bar does exactly what it’s supposed to: submenus drop down and function perfectly, by opening to the right side and linking appropriately. With one particular submenu, the sub-submenus open right on top of the submenu. Can’t figure out why, the sub-submenus are configured precisely like the sub-submenus that open correctly, i.e. on the right.

Help?

The site is https://www.sfvaudubon.org — the menu is “Go Birding” and the submenu whose sub-submenus are misbehaving is the bottom one, “SFV Backyard Bird Identification.”