Why does shift-queuing blink have unpredictable results?

I was messing around with some of the "Challenge" missions and discovered a Protoss a mechanic that I don't quite understand (Protoss is my least played race by far, so sorry if this is a basic question).

When I attempt to blink stalkers using the shift-queuing method, I usually end up leaving some stalkers behind. It's odd that sometimes all stalkers will properly blink but sometimes I'll end up leaving somewhere between 1-3 stalkers behind. The unpredictability is unsettling...

Mechanically, I'm going through the following 3 steps, which I believe are the correct ones:

• First, I select the stalkers, right click on the location from which I want to initiate the blink
• Then I press Shift + R (R is my blink hotkey) and left-click on the intended destination of the blink
• Lastly, I release shift, then press Shift + right-click on a location to which newly blinked stalkers can go (so as to make room for the stalkers which haven't yet blinked).

Note: this is the same series of steps as outlined in this other post.

Here's a gif showing the result (for some reason, it's giving me an error when I try to upload an image directly to my post).

What am I doing wrong?

Alternatively, if I'm following the right steps, what is causing the unpredictability? I have never seen an instance of a unit simply "skipping" one of the commands in its command-queue and attempting to execute the next one...