dcolumn decimal column format breaks file

Question

AI'm having trouble using the dcolumn decimal format, The file looks like this:

But as soon as I add the formatting in the tabular* in \begin{tabular*}{\textwidth}{@{\extracolsep{\fill}} l *{4}{d{3.6}} @{}} it wont compile and points to a missing } which is not the case unless I should add and extra one. If I understood correctly the formatting *{4}{d{3.6}} should give 4 columns 3 spaces before the decimal period and 6 after the decimal period to give space for the order of magnitude. Some of my code is based on the first answer to this question.

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EDIT: This example had errors unrelated to the behavior of dcolumn as pointed by @Rmano. Each circuitikz environment was lacking a semicolon ; at the end of the last line. A better MWE was provided by @David Carlisle in the comments and his answer below.

\documentclass[letter]{article}
\usepackage[utf8]{inputenc}
\usepackage[T1]{fontenc}
\usepackage[spanish,es-tabla]{babel}
\usepackage{mathrsfs}
\usepackage{amsmath}
\usepackage{amssymb}
\usepackage{tikz}
\usepackage[oldvoltagedirection]{circuitikz}
\usepackage{pgfplots}
\pgfplotsset{compat=1.15}
\usetikzlibrary{arrows}
\pagestyle{empty}
\usepackage{booktabs}
\usepackage{caption}
\usepackage{subcaption}
\captionsetup{  singlelinecheck=false,
        font=footnotesize,
        labelfont=bf}
\usepackage{dcolumn}
\newcolumntype{d}[1]{D{.}{.}{#1}}
\title{\textbf{Impedancia}}
\author{}
\date{}
\begin{document}
\maketitle
\section{Circuitos RC}
\begin{figure}[ht]
    \centering
    \begin{subfigure}[t]{0.32\textwidth}
        \centering
        \begin{circuitikz}[scale=0.7, transform shape,font=\small]
        \draw (0,2)
        to[R=$R_s$, o-] (2,2)
        to[C= $C_s$] (2,0)
        to[short, -o] (0,0)
        \end{circuitikz}    
    \label{fig:a}
    \end{subfigure}
    \begin{subfigure}[t]{0.32\textwidth}
        \centering
        \begin{circuitikz}[scale=0.7, transform shape,font=\small]
        \draw (0,2) to[short, o-] (2,2)
        to[short] (4,2)
        to[C= $C_p$] (4,0)
        to[short, -o] (0,0)
        (2,2) to[R= $R_p$] (2,0)
        \end{circuitikz}    
    \label{fig:b}
    \end{subfigure}
    \begin{subfigure}[t]{0.32\textwidth}
        \centering
        \begin{circuitikz}[scale=0.7, transform shape,font=\small]
        \draw (0,2) to[R=$R_s$,o-] (2,2)
        to[short] (4,2)
        to[C= $C_p$] (4,0)
        to[short, -o] (0,0)
        (2,2) to[R= $R_p$] (2,0)
        \end{circuitikz}    
    \label{fig:c}%
    \end{subfigure}

\caption{a) Circuito RC serie. b) Circuito RC paralelo. c) Circuito RC paralelo con resistencia en serie. $R_s=R_p=1k\Omega$, $C_s=C_p=1\mu F$}
\label{fig:RC}%
\end{figure}
\section{Cálculos de Impedancia}

\begin{table}[h]
    \footnotesize
    \begin{tabular}{\textwidth}{@{\extracolsep{\fill}} l {4}{d{3.6}} @{}}
        \toprule
    & \multicolumn{4}{l}{\textit{Frecuencia}} \
    & \multicolumn{1}{l}{$10 Hz$} & \multicolumn{1}{l}{$100 Hz$} & \multicolumn{1}{l}{$1 kHz$} & \multicolumn{1}{l}{$10 kHz$} \
    \midrule
    \multicolumn{5}{l}{\textit{Circuito 1}} \
    $Z_1 (\Omega)$  & 1.59e+04 & 1.88e+03 & 1.01e+03 & 1.00e+03 \
    $\theta_1$  & -86.40 & -57.86 & -9.04 & -0.91 \
    \multicolumn{5}{l}{\textit{Circuito 2}} \
    $Z_2 (\Omega)$  & 1.00e+03 & 0.85.e+03 & 0.16e+03 & 1.59e+01 \
    $\theta_2$  & -3.60 & -32.14 & -80.96 & -89.09 \
    \multicolumn{5}{l}{\textit{Circuito 3}} \
    $Z_3 (\Omega)$  & 2.00e+03 & 1.78e+03 & 1.03e+03 & 1.00e+03 \
    $\theta_3$  & -1.80 & -14.70 & -8.61 & -0.91 \
    \bottomrule
    \end{tabular*}
    \caption{Impedancia y ángulo de fase versus frecuencia}
\end{table}
\end{document}

Answer 1

A simpler example not showing unrelated errors is

\documentclass{article}
\usepackage[spanish]{babel}
\usepackage{dcolumn}
\newcolumntype{d}[1]{D{.}{.}{#1}}
\begin{document}
\noindent
\begin{tabular}{\textwidth}{@{\extracolsep{\fill}} l d{3.6} @{}}
    a & 1.59e+04 
\end{tabular}
\end{document}

Which produces

! Missing } inserted.
<inserted text> 
                }
l.10     a & 1
              .59e+04
? 

the spanish option modifies . you can prevent that with

\documentclass{article}
\usepackage[spanish,es-nodecimaldot]{babel}
\usepackage{dcolumn}
\newcolumntype{d}[1]{D{.}{.}{#1}}
\begin{document}
\noindent
\begin{tabular}{\textwidth}{@{\extracolsep{\fill}} l d{3.6} @{}}
    a & 1.59e+04 
\end{tabular}
\end{document}

If you need the spanish decimaldot option but just a normal . here, I couldn't see a defined way (the usual babel \shorhandoff mechanism to locally disable changes dos not work for this definition)