Why the \section*{Past History} and \section*{Present problem} are compiling differently?

Why the \section*{Past History} and \section*{Present problem} are compiling differently in a following code? The present problem is getting indented on compiling.

   \documentclass[a4paper]{exam}
\usepackage{multicol}
\usepackage{multicol}
\setlength\columnsep{40pt}
\begin{document}

\begin{center}
\fbox{\fbox{\parbox{5.5in}{\centering
OPD ENCOUNTER FORM}}}
\end{center}
\vspace{0.1in}

\makebox[\textwidth]{Name :\enspace\hrulefill}
\begin{multicols}{2}
\vspace{0.2in}
\makebox[0.45\textwidth]{Age:\enspace\hrulefill}
\makebox[0.5\textwidth]{Sex:\enspace\hrulefill}
\end{multicols}
\makebox[\textwidth]{Address:\enspace\hrulefill}

\begin{multicols}{2}
\makebox[0.45\textwidth]{City: \enspace\hrulefill}
\makebox[0.45\textwidth]{Ref: \enspace\hrulefill} 
\end{multicols} 
%
%Past and family history 
\section* {Past History}

\begin{questions}
\question Significant past history 
\begin{oneparcheckboxes}
\choice Yes \choice No \choice Previously noted 
\end{oneparcheckboxes} 
\begin{multicols}{2}

\question Diabetes Mellitus \hrulefill

        \begin{oneparcheckboxes}

                \choice   Nephropathy
                \choice Retinopathy
                \choice Neuropathy
                \choice NASH
                \choice Gastroparesis
         \end{oneparcheckboxes}
\question Systemic hypertension
\begin{oneparcheckboxes}    
        \choice \hrulefill    
\end{oneparcheckboxes}
\question Ischemic heart disease 
\begin{oneparcheckboxes} \choice since  \hrulefill 
\choice Angioplasty \choice CABG \choice medical management
\end{oneparcheckboxes}


\question Tuberculosis  \hrulefill 
\begin{oneparcheckboxes}
\choice PTB \choice Peritoneal  \choice intestinal \choice Other \hrulefill 
\end{oneparcheckboxes} 

\question Hypothyroidism 
\begin{oneparcheckboxes}
\choice \hrulefill 
\end{oneparcheckboxes} 
%---
\question CVE 
\begin{oneparcheckboxes}
\choice Ischemic \choice Bleed \hrulefill 
\end{oneparcheckboxes} 
%---
\question Surgery 
\begin{oneparcheckboxes}
\choice Cholecystectomy \choice appendectomy \choice hysterectomy \choice other \hrulefill 
\end{oneparcheckboxes}

%---
\question Endoscopic procedure
\begin{oneparcheckboxes}
\choice UGI \hrulefill 
\choice Colonoscopy \hrulefill
\choice     Ercp \hrulefill 
\end{oneparcheckboxes} 
%---
\question GI Diseases
\begin{checkboxes}
\choice GERD \hrulefill 
\choice IBS \hrulefill 
\choice Ulcer Ds \hrulefill 
\choice Chr. constipation \hrulefill 
\choice Idiopathic ulcerative colitis \hrulefill 
\choice Gall stone disease \hrulefill 
\choice Cirrhosis of liver
\begin{oneparcheckboxes}
\choice Alc  \choice NASH  \choice Hep B \choice Hep C \choice AIH \choice Wilson \choice Cryptogenic \choice Other 
\end{oneparcheckboxes} \\
\begin{oneparcheckboxes}
\choice Ascites \choice SBP \choice HE \choice HRS \choice Variceal bleed 
\end{oneparcheckboxes}
\choice malignancy. Sp. \hrulefill 
\end{checkboxes} 
\end{multicols}

\section* {Present Problem}
\fillwithlines{0.5in}
\end{questions}



\end{document}