HiDPI mode first icon is squashed vertically
In gnome-tweak-tool set window scaling to 2 and the leftmost icon is squashed vertically. The highlight appears to be for the next lower icon size to the rest of the dock and the icon itself is scaled vertically. (Gnome Version 3.14.1, simple-doc git 39b850)

same problem, gnome 3.16.1
same problem, gnome 3.18
I've got two computers running 3.18.2, but this problem appears only on one of them...
Could anyone confirm if this bug is present or not also in dash-to-dock, extension from which this is derived? This might help finding the fix.
@micheleg : I tried dash-to-dock on the computer on which the leftmost icon was squashed vertically and the bug is not present.
So this is not solved yet?
This issue is still present in the latest release. It is not present in dash-to-dock.