Duplicate warning message into biber log (.blg)

[matteofg]

I set a personal datamodel to define a mandatory field. Below a mwe:

\begin{filecontents}[overwrite]{\jobname.bib}
@customa{a,
  author = {Author},
  %title = {Title}, % mandatory field
}
\end{filecontents}

\begin{filecontents}[overwrite]{\jobname.dbx}
\DeclareDatamodelEntrytypes{customa}

\DeclareDatamodelEntryfields[customa]{author, title}

\DeclareDatamodelConstraints[customa]{
  \constraint[type=mandatory]{
    \constraintfield{title}
  }
}
\end{filecontents}

\documentclass{article}
\usepackage[datamodel=\jobname]{biblatex}
\addbibresource{\jobname.bib}

\DeclareBibliographyDriver{customa}{%
  \usebibmacro{author}%
  \newunit\newblock
  \usebibmacro{title}%
  \usebibmacro{finentry}}

\begin{document}
\cite{a}
\printbibliography
\end{document}

Note that I commented the mandatory field title.
Running biber --validate-datamodel the same warning message appears twice in the .blg file:

WARN - Datamodel: customa entry 'a' (test.bib): Missing mandatory field 'title'
WARN - Datamodel: customa entry 'a' (test.bib): Missing mandatory field 'title'
INFO - WARNINGS: 2

Why does biber recognize two warnings (instead of one)?

[plk]

Please try the development of biber from Sourceforge.

[matteofg]

The fix works correctly. Thanks.