The issue is fixed by adding `zle redisplay` after `zle
expand-and-complete` for the expand-and-complete key binding. An
additional `print -n '...'` is also included to show an indicator while
the menu is loading, and that is purely cosmetic.
There's still one glitch: the prompt jumps one line up after
<Tab><Tab><Ctrl-C>. This was observed in Prezto too.