Wrong numbering of table with multiple tabular environments

Question

When there are multiple longtabu environments in a talbe, the numbering of table will be wrong. See the MWE below.

\documentclass{article}
\usepackage{caption}
\usepackage{subcaption}
\usepackage{tabularx}
\usepackage{tabu}
\usepackage{longtable}
\begin{document}


\begin{table}
\centering
\caption{An interesting table}
\subcaption*{Panel A: Some stuff}
\begin{longtabu}{XXX}
First name & Last name  & Product \\
Bubba & Gump & Shrimp \\
Steve & Jobs & Happiness \\
\end{longtabu}
\bigskip
\subcaption*{Panel B: Other stuff}
\begin{longtabu}{XX}
School & State \\
Harvard & MA \\
Yale & CT \\
Brown & RI \\
\end{longtabu}
\end{table}


\begin{longtabu}{ll}

    Longtable & Longtable \\
    Longtable & Longtable \\
    Longtable & Longtable \\
    Longtable & Longtable \\
    Longtable & Longtable \\
    \caption{This is a caption}
\end{longtabu}

\end{document}

Answer 1

As Ulrike Fischer already mentioned in the comments, using longtabu inside of a table environment does not make sense.

If you use tabularx or a simple tabular instead of the longtabu the tables are numbered correctly, For the second longtabu in your code, I have used longtable and placed the corresponding caption in the beginning so that it is displayed above the longtable:

\documentclass{article}
\usepackage{caption}
\usepackage{subcaption}
\usepackage{tabularx}
\usepackage{longtable}
\begin{document}

\begin{table}
\centering
\caption{An interesting table using tabularx}
\begin{subtable}{\textwidth}
\subcaption*{Panel A: Some stuff}
\begin{tabularx}{\textwidth}{XXX}
First name & Last name  & Product \\
Bubba & Gump & Shrimp \\
Steve & Jobs & Happiness \\
\end{tabularx}
\end{subtable}
\bigskip

\begin{subtable}{\textwidth}
\subcaption*{Panel B: Other stuff}
\begin{tabularx}{\textwidth}{XX}
School & State \\
Harvard & MA \\
Yale & CT \\
Brown & RI \\
\end{tabularx}
\end{subtable}
\end{table}


\begin{longtable}{ll}
\caption{This is a caption of a longtable}\\
\endhead
    Longtable & Longtable \\
    Longtable & Longtable \\
    Longtable & Longtable \\
    Longtable & Longtable \\
    Longtable & Longtable \\
\end{longtable}



\begin{table}[htbp]
\caption{An interesting table using tabular}
\begin{subtable}{\textwidth}
\centering
\subcaption*{Panel A: Some stuff}
\begin{tabular}{lll}
First name & Last name  & Product \\
Bubba & Gump & Shrimp \\
Steve & Jobs & Happiness \\
\end{tabular}
\end{subtable}
\bigskip

\begin{subtable}{\textwidth}
\centering
\subcaption*{Panel B: Other stuff}
\begin{tabular}{ll}
School & State \\
Harvard & MA \\
Yale & CT \\
Brown & RI \\
\end{tabular}
\end{subtable}
\end{table}


\end{document}