I had this issue after upgrading to 11x add-in (upgraded from 7.1.3), but I only had two instances of the Essbase menu dropdown. I noticed the excel add-ins menu had duplicate essexcln.xll checkboxes.
I think forum member Angie had recommended uninstalling all remnants of the prior EB versions before installing the latest one. So I went back and uninstalled everything, including removing the environment variables, removed the c:\Hyperion folder and made sure all of the Add-ins folder did not have any essexleqd.xla/essexcln.xll (I think thats how you spell it) straglers remaining in the excel Add-ins folder.
Once I reinstalled the latest version, problem went away. So far so good.