My workflow includes typing shortcut upon which KM presents input form with various popup menus. First one is focused, so I can press space to open the menu, however once I do that, keyboard is no longer accepted - the only way out of it is to use mouse.
Interestingly, if I click on an option, or click out on underlying form to close the menu, from that moment on, I can use keyboard fully - I can open the menu with space and then use arrows and enter to select desired option. However when I confirm the form, and invoke it again, the same happens. Feels as if the form somehow looses focus upon opening popup menu... This happens consistently on both my macs.
Example of a form: