Why does touch bar sometimes ignore first touch?
This has been an issue since precisely macOS High Sierra beta 3. In the release notes for this pre-release update1, ‘heuristics’ were updated with regard to preventing accidental Touch Bar inputs.

Since that update, pressing the Touch Bar too soon after another keyboard input too close to the Touch Bar will invalidate the Touch Bar press. The key will illuminate but only very briefly and the input will not pass. It is then necessary to press the key again for it to go through. Notice the difference between q-esc and 1-esc.



According to event viewer I observed while recording that video,


4 of the 5 q-esc presses passed through the esc
(the last press I slightly missed the activation area of esc, which was something else mentioned in the release notes: the activation areas were reduced in from the edges), and
0 out of 5 1-esc presses passed through the esc.


I installed macOS updates on my external disk first and I could instantly replicate this issue when using beta 3 and had no problem with beta 2.

I filed a radar per the instructions given in the release notes for anyone who had feedback for this change, with my view of the problem this change made for people who are more accurate with their Touch Bar key presses. Unfortunately, this radar was closed as won't be fixed.

It is my impression this delay is a feature: part of the remedy for people who provide spurious inputs to the Touch Bar, which was something complained about constantly on virtually all the reviews I read and watched, yet not something I've ever experienced myself.

1 Even though High Sierra is released, I am unsure as to whether the release notes for pre-release versions of macOS can be reproduced here for those who are not part of the developer programme.