There should never be two of the same rows in the dopesheet! I'd like to get this fixed ASAP, as it could corrupt your project files.
I tried to reproduce, but found it to work correctly. 🙁 Can you provide reproduction steps using one of the example projects? Eg, open goblins, select what keys, copy, paste where, expected result vs actual result.
One confusion may be pasting to a different bone. If you select keys from a single bone, it will paste to whatever bone is selected. If you have some other bone selected, box select some keys from a single bone, then paste, you may not notice that the keys were pasted to a different bone! Two rows showing up in the dopehsheet is just plain broken though, so hopefully we can find some clues how that happens.