line gaps visible in table

Question

I am having some gaps when I use hline or cline in latex, here are examples of my code:

\begin{table}[ht]
    \centering      %{*4l}
\begin{tabular}{|c|c|c|c|c|}%{p{0.22\textwidth}p{0.15\textwidth}p{0.15\textwidth}p{0.15\textwidth}p{0.15\textwidth}}
\toprule
Model & \multicolumn{4}{|c|}{Operation points}  \\\midrule
& $\varepsilon= 1\%$ & $\varepsilon= 3\%$ & $\varepsilon= 5\%$ & $\varepsilon= 9\%$ \\\cline{2-5}
% \emph{Model} & \emph{Operating Points- IGVF ($\varepsilon$)} &&&  \\\midrule
    EE2F Monodisperse & x & x & x & - \\\hline
    EE2F MUSIG & x & x & x & - \\\hline
    Hybrid Monodisperse & x & x & x & \\\hline
    H2P MUSIG & x & x & x & \\
    \bottomrule
\end{tabular}
\\\raggedright Note: $d_B$= $0.25\,\mathrm{mm}$ in the Monodisperse modeling.
    \caption{Simulation models used for the gas-laden flow modeling.}
    \label{tab:operation-points-gas-laden}
\end{table}

also:

    \centering
    \begin{tabular}{|c|c|c|c|c|c|}    \toprule
    $\varepsilon (\%)$ & \multicolumn{5}{|c|}{$Q_t (\mathrm{m^3})$} \\
    \midrule
        0 \% & 15.0 & 34.0 & 68.0 & 102.0 & 120.0 \\\bottomrule
    \end{tabular}
    \caption{Operation points investigated by the single-phase simulation}
    \label{tab:operation-points-single-phase}
\end{table}

What is the problem? Thanks!