I've got the same error in Emacs built from master via homebrew --HEAD on latest macOS.
Here is a video https://youtu.be/I8rEwM-9gsY
I was running it with
I am seeing the same issue running the latest MELPA version:
On mac osx using Emacs 25.2.1.
Question: Previously, a single tab used to also work but now to tab strokes are required to select the completion... was the old behavior changed?