BibLaTeX: citing two authors sometimes shows incorrect results in 2021 Journal of Finance bibliographic style

Question

I have two questions when I use a biblatex template from https://tex.stackexchange.com/questions/379901/biblatex-how-to-match-the-journal-of-finance-bibliographic-style.

1. It sometimes shows incorrect result when I want to cite an article with two authors, for example

P. Jain and S. Jain (2019).

The correct result should be

Jain and Jain (2019).

However, this rarely happens, so I'm not sure about the triggering mechanism.

2. My citation (/parencite) is without parenthesis around the year.

(Sharpe, 1964).

I hope the correct result be

(Sharpe, (1964)).

How do I change my biblatex setting?

\usepackage{csquotes} 
\usepackage[style=authoryear, 
backend=biber, 
giveninits=true,
uniquelist = false, 
uniquename=init,
isbn=false, 
maxcitenames=3,
dashed=false, 
maxbibnames=999,
doi=false,
url=false]{biblatex}
\addbibresource{Auto Rebalance_ref.bib} %Imports bibliography file
\DeclareDelimFormat{nameyeardelim}{\addcomma\space}
\DeclareNameAlias{sortname}{family-given}
\renewcommand*{\labelnamepunct}{\addspace}
\DeclareFieldFormat
  [article,inbook,incollection,inproceedings,patent,thesis,unpublished]
  {title}{#1}
\DeclareFieldFormat{titlecase}{\MakeSentenceCase*{#1}}
\renewbibmacro*{in:}{%
  \ifentrytype{article}
    {\setunit{\addcomma\space}}
    {\printtext{\bibstring{in}\intitlepunct}}}
\DeclareFieldFormat{journaltitlecase}{#1}
\renewbibmacro*{journal}{%
  \ifboolexpr{
    test {\iffieldundef{journaltitle}}
    and
    test {\iffieldundef{journalsubtitle}}
  }
    {}
    {\printtext[journaltitle]{%
       \printfield[journaltitlecase]{journaltitle}%
       \setunit{\subtitlepunct}%
       \printfield[journaltitlecase]{journalsubtitle}}}}
\renewbibmacro*{volume+number+eid}{%
  \printfield{volume}%
  \setunit{\addcomma\space}%
  \printfield{eid}}
\DeclareFieldFormat[article,periodical]{volume}{\mkbibbold{#1}}% volume of a journal
\DeclareFieldFormat{pages}{#1}

@article{jain2019can,
  title = {Can {{Machine Learning}}-{{Based Portfolios Outperform Traditional Risk}}-{{Based Portfolios}}? The {{Need}} to {{Account}} for {{Covariance Misspecification}}},
  shorttitle = {Can {{Machine Learning}}-{{Based Portfolios Outperform Traditional Risk}}-{{Based Portfolios}}?},
  author = {Jain, Prayut and Jain, Shashi},
  date = {2019-09},
  journaltitle = {Risks},
  volume = {7},
  number = {3},
  pages = {74},
  publisher = {{Multidisciplinary Digital Publishing Institute}},
  urldate = {2021-09-28},
  issue = {3},
  langid = {english}
}

@article{dai2002efficient,
  title = {Efficient, Exact Algorithms for Asian Options with Multiresolution Lattices},
  author = {Dai, Tian-Shyr and Lyuu, Yuh-Dauh},
  date = {2002-05-01},
  journaltitle = {Review of Derivatives Research},
  shortjournal = {Review of Derivatives Research},
  volume = {5},
  number = {2},
  pages = {181--203},
  urldate = {2021-10-13},
  langid = {english}
}

Answer 1

Use

• uniquename=false to prevent typesetting initials for unique names of authors in the label
• giveninits=true to allow for using given initials in the bibliography
• \DeclareInnerCiteDelims{cite}{\bibopenparen}{\bibcloseparen} to customize brackets around the year

MWE

\begin{filecontents*}{Auto Rebalance_ref.bib}
    @article{jain2019can,
        title = {Can {{Machine Learning}}-{{Based Portfolios Outperform Traditional Risk}}-{{Based Portfolios}}? The {{Need}} to {{Account}} for {{Covariance Misspecification}}},
        shorttitle = {Can {{Machine Learning}}-{{Based Portfolios Outperform Traditional Risk}}-{{Based Portfolios}}?},
        author = {Jain, Prayut and Jain, Shashi},
        date = {2019-09},
        journaltitle = {Risks},
        volume = {7},
        number = {3},
        pages = {74},
        publisher = {{Multidisciplinary Digital Publishing Institute}},
        urldate = {2021-09-28},
        issue = {3},
        langid = {english}
    }
\end{filecontents*}
\documentclass{book}
\usepackage{csquotes} 
\usepackage[style=ext-authoryear,uniquename=false,giveninits=true]{biblatex}
\addbibresource{Auto Rebalance_ref.bib}
\DeclareInnerCiteDelims{cite}{\bibopenparen}{\bibcloseparen}
\begin{document}
\cite{jain2019can}

\printbibliography[heading=subbibliography]


\end{document}

Edit

To allow for customizing brackets for \parencite, you may need to redefine it as follows

\DeclareInnerCiteDelims{parencite}{\bibopenparen}{\bibcloseparen}
\DeclareOuterCiteDelims{parencite}{\bibopenparen}{\bibcloseparen}

parentracker option (which is true by default) keeps tracking of nested parentheses and brackets and automatically changes them when detecting nested parentheses and brackets of similar type. This default behavior is desirable because citations become more readable. However, if you still want parentheses for the label and the year to still be nested you need to set parentheses=false when loading biblatex

\begin{filecontents*}{Auto Rebalance_ref.bib}
    @article{jain2019can,
        title = {Can {{Machine Learning}}-{{Based Portfolios Outperform Traditional Risk}}-{{Based Portfolios}}? The {{Need}} to {{Account}} for {{Covariance Misspecification}}},
        shorttitle = {Can {{Machine Learning}}-{{Based Portfolios Outperform Traditional Risk}}-{{Based Portfolios}}?},
        author = {Jain, Prayut and Jain, Shashi},
        date = {2019-09},
        journaltitle = {Risks},
        volume = {7},
        number = {3},
        pages = {74},
        publisher = {{Multidisciplinary Digital Publishing Institute}},
        urldate = {2021-09-28},
        issue = {3},
        langid = {english}
    }
\end{filecontents*}
\documentclass{book}
\usepackage{nicematrix}
\usepackage{csquotes} 
\usepackage[
style=ext-authoryear,uniquename=false,giveninits=true,
parentracker=false]{biblatex}
\addbibresource{Auto Rebalance_ref.bib}
\DeclareInnerCiteDelims{cite}{\bibopenparen}{\bibcloseparen}
\DeclareOuterCiteDelims{cite}{\bibopenbracket}{\bibclosebracket}
\DeclareInnerCiteDelims{parencite}{\bibopenparen}{\bibcloseparen}
\DeclareOuterCiteDelims{parencite}{\bibopenparen}{\bibcloseparen}
\begin{document}
\begin{NiceTabular}{c l}
\cite{jain2019can} & with \verb|\cite|
\\

\parencite{jain2019can} & with \verb|\parencite|
\\


\end{NiceTabular}
\printbibliography[heading=subbibliography]
\end{document}