\documentclass[tikz]{standalone}
\usepackage{pgfplots}
\pgfplotsset{compat=newest} % <-- Causes dancing y label when adding 'extra y ticks'
\pgfplotsset{myDefaultStyle/.style =
{
width = 160mm,
height = 90mm,
axis x line = bottom,
axis y line = left,
ylabel = y Label,
xlabel = x Label,
grid = major,
}}
\begin{document}
% ######### Plot #########
% ########################
\begin{tikzpicture}
\begin{axis}[
myDefaultStyle,
xmin = 0,
xmax = 32,
ymin = 24.5,
ymax = 30.1,
xtick = {0,10,20,30},
ytick = {25,26,30},
]
% Plots
\addplot[domain=0:10,red]{x^2};
%
\end{axis}
\end{tikzpicture}
% ######### Plot #########
% ########################
\begin{tikzpicture}
\begin{axis}[
myDefaultStyle,
xmin = 0,
xmax = 32,
ymin = 24.5,
ymax = 30.1,
xtick = {0,10,20,30},
ytick = {25,26,30},
extra y ticks={25.5}, % <-- Added
]
% Plots
\addplot[domain=0:10,red]{x^2};
%
\end{axis}
\end{tikzpicture}
\end{document}

forget your password?thing (no email so far). Would you also consider it a bug? Maybe you can copy and paste the code to sf. – Dr. Manuel Kuehner Jun 16 '17 at 16:05