I confirmed the issue. The recording works ok, but on replay the menu does not open, even so it was selected ok (just as you said).
(Maybe there is a solution with Selenium IDE commands, but with my tests I have not found any, just like you. If you or anyone else still find one, please let me know.)
If you are on Windows, I highly recommend that you use SeeShell and its purely image-driven approach, this will make this web automation task much easier.
If you are on Mac and Linux, stay tuned for future Kantu updates that bring some parts of the SeeShell technology to Kantu in a cross-platform way.