I have this MWE. On transition 3 one of the squares is thicker. Unfortunately it is invisible before that transition. How can I make it look normal on transition 2 and then have a thick border on transition 3?

```
\documentclass[11pt]{beamer}
\usepackage{amsmath, amssymb, graphicx}
\usepackage[]{algorithm2e}

\usepackage{tikz}
\usetikzlibrary{arrows.meta, calc, matrix, positioning, overlay-beamer-styles}

\newcommand\Circle[1]{%
	\tikz[baseline=(char.base)]\node[circle,draw,inner sep=2pt] (char) {#1};}

\tikzset{circled/.style={path picture={
			\draw let \p1=($(path picture bounding box.north east)-(path picture bounding
			box.south west)$),\n1={min(\x1,\y1)/2.2} in
			(path picture bounding box.center) circle[radius=\n1];}},
	circled on/.style={alt=#1{circled}{}}}

\begin{document}

\begin{frame}[fragile,t]
    \frametitle{
        \only<1-2>{Title}
    }
\begin{center}
    \begin{tikzpicture}
    \matrix (m) [matrix of nodes,
    nodes={draw, minimum size=8mm},
    column sep=3mm,
    row sep=2mm,
    row 7/.style={visible on=<2->},
    row 1/.style={nodes={draw=none}},
    row 7 column 2/.style={nodes={draw, line width=1.2pt}, visible on=<3>}] (mat)
    {
        0 & 1 & 2 & 3 & 4   \\[-3mm]
        6 & 2 & 4 & 4 & 5   \\
        |[circled on=<2>]| 8 & 4 &  |[circled on=<{2-}>]| 5 & 6 &  |[circled on=<2->]| 6   \\
        7 & 5 & 2 & 7 & 5   \\
        6 & 5 & 1 & 6 & 5   \\
        5 & |[circled on=<2->]| 9 & 0 & 2 & 4   \\
        8 & 9 & 5 & 7 & 6   \\
    };
    \path (mat-6-1.south) -- (mat-7-1.north) coordinate[midway](aux);
    \draw[visible on=<2->] (mat.west|-aux) -- (mat.east|-aux);
    \node[overlay,right=1.5cm of mat-7-5.east, visible on=<2->,align=left] (label) {Two\\ lines};
    \draw[overlay,->, thick, visible on=<2->] (label.west) -- ++(-1, 0);
    \node[overlay,left=1.5cm of mat-7-1.east, visible on=<3>,align=left] (label) {Text};
    \end{tikzpicture}
\end{center}

\end{frame}

\end{document}
```