Biblatex in beamer not adding extradate letter

Question

I am using biblatex in beamer to manage both my bibliography and my in-text citations after having read the following post: How to cite a reference on Beamer as (author, year).

However, I am left with one problem I am not able to solve:

1. I have two identical author-year documents, and biblatex is not inserting an extra letter after the year to differentiate the two (both in the in-text citation and in the bibliography):

What I would like to have is:

• (BCBS, 2013a)
• (BCBS, 2013b, 2014)

The same in the bibliography.

Here is the code of the text file:

\documentclass{beamer}
\usepackage[utf8]{inputenc}
\usepackage[T1]{fontenc}
\usepackage{dirtytalk}
\usepackage{amsfonts}
\usepackage{amssymb}
\usepackage{amsthm}
\usepackage{enumerate}
\usepackage{scalerel}
\usepackage[export]{adjustbox}
\usepackage{caption}
\usepackage{graphicx}
\usepackage[bibstyle=apa, citestyle = apa, backend=bibtex]{biblatex}
\addbibresource{Bibliography/Library_New}
\renewcommand{\nameyeardelim}{\addcomma\addspace} 
\renewcommand{\bibfont}{\tiny}
\usepackage{hyperref}
\hypersetup{
    colorlinks,
    linkcolor={},
    citecolor={blue},
    urlcolor={blue}
}
\setbeamertemplate{footline}[frame number]
\usefonttheme{structuresmallcapsserif}
\usecolortheme{rose}
\newenvironment{trienv}{\only{\setbeamertemplate{items}[triangle]}}{}
\newenvironment{squareenv}{\only{\setbeamertemplate{items}[square]}}{}
\usepackage{booktabs}
\usepackage{dcolumn} 
\usepackage{rotating}
\beamertemplatenavigationsymbolsempty
\begin{document}
{
\setbeamertemplate{headline}{}
\begin{frame}[noframenumbering, plain]
\titlepage
\end{frame}
}
\begin{frame}{Citations}
In text: 
\begin{itemize}
    \item \parencite{BCBS_RCAP2013_RWA}
    \item \parencite{BCBSNewMotto2013,BCBSNewMotto2014}
\end{itemize}
\printbibliography[sorting=nty]
\end{frame}
\end{document}

and the code of the bib file:

@techreport{BCBSNewMotto2013,
author = {{BCBS}},
address = {Basel, Switzerland},
institution = {Bank for International Settlements},
isbn = {9291319406},
number = {October},
pages = {1--23},
title = {{Discussion paper - The regulatory framework: balancing risk sensitivity, simplicity and comparability}},
url = {https://www.bis.org/publ/bcbs258.htm},
year = {2013}
}
@techreport{BCBS_RCAP2013_RWA,
author = {BCBS},
institution = {Bank for International Settlements},
address = {Basel, Switzerland},
abstract = {This document is called BCBS 256. This is where it all started (Basel IV). This document outlines for the first time "formally" the huge variability registered within the RWA computations across banks.},
isbn = {929131966X},
keywords = {BCBS},
number = {October},
pages = {57},
title = {{Regulatory Consistency Assessment Programme (RCAP) – Analysis of risk-weighted assets for credit risk in the banking book}},
year = {2013}
}
@techreport{BCBSNewMotto2014,
abstract = {This document is called BCBS 306. This document introduces for the first time the motto: greater simplicity, comparability and risk sensitivity of the risk-weighted assets computations.},
address = {Basel, Switzerland},
author = {{BCBS}},
isbn = {9789291973804},
keywords = {BCBS},
number = {December 2014},
pages = {12},
institution = {{Bank for International Settlements}},
title = {{Consultative document - Capital floors: the design of a framework based on standardised approaches}},
year = {2014}
}

Any idea why this could be, and how I might solve it?

Thanks a lot!