Garbled Multi-Dropdown List (Backend Admin)

has anyone run into an issue like the attached screencap on the Backend/Admin in ES creating MultiDropdown List fields und Profile Type? After a certain number of items input as field selection options i get an overlay from somewhere that makes the field list area i'm building inaccessible (can't access the field inputs, can drag/drop them to new locations). It happens on any and all multi-dropdown lists I try to create, after reaching the 10th item input - not sure how to describe this in words really so, screencap it is!

* i can provide some backend access if it truly becomes necessary