\"\shorthandon{"}\" an falscher Stelle

ptbletter/ptbletter.cls

-% Rolf Niepraschk, Rolf.Niepraschk@ptb.de
+% Rolf Niepraschk, Rolf.Niepraschk@gmx.de
 
 \setcounter{errorcontextlines}{100}  \listfiles
 
 \NeedsTeXFormat{LaTeX2e}[1999/12/01]
-\ProvidesClass{ptbletter}[2021/06/04 v0.4b PTB-Brief-Klasse (RN)]
+\ProvidesClass{ptbletter}[2023/04/21 v0.4c PTB-Brief-Klasse (RN)]
 
 \let\ptb@tempdima=\@ovxx
 \let\ptb@tempdimb=\@ovyy
@@ -113,16 +113,15 @@
 \RequirePackage[\ptb@lang]{babel}
 \RequirePackage{etoolbox,iflang,trimspaces}
 \AtEndPreamble{%
-  \IfLanguageName{ngerman}{
-    \AtEndOfClass{\shorthandon{"}}
+  \IfLanguageName{ngerman}{%
     \RequirePackage[autostyle=true,german=guillemets,maxlevel=3]{csquotes}%
   }{%
     \RequirePackage[babel=once]{csquotes}
     \useshorthands*{"}
-  }
+  }%
   \MakeAutoQuote{»}{«}
   \defineshorthand{"`}{\openautoquote}
-  \defineshorthand{"'}{\closeautoquote}
+  \defineshorthand{"'}{\closeautoquote}\shorthandon{"}
 }
 
 \AtEndOfClass{%
@@ -132,8 +131,6 @@
   }%
 }
 
-%%%\AtEndOfClass{\shorthandon{"}}
-
 \setplength{toaddrhpos}{72bp}
 \setplength{toaddrvpos}{124bp}
 
@@ -372,6 +369,7 @@
     ,babel=true
     ]{microtype}
   \fi
+  \shorthandon{"}%
 }
 \RequirePackage{enumitem}
 \setlist{leftmargin=*,nosep,topsep=.5em,itemsep=.25em}