Biblatex biblography prints all caps letters when using UTF8 special characters

Question

I use biblatex with a biber backend and the usepackage[utf8]{inputenc} package. For some reason, references in my .bib file that contain special characters are printed in all-caps in my bibliography.
I tried replicating the effect with a MWE, however every version I tried printed the bibliography in a correct way. Does anyone know of a combination of packages that could cause this behavior?
EDIT: MWE replicating the effect
RequirePackage{filecontents}

begin{filecontents*}{mybib.bib}
@book{test1,
    address = {City},
    title = {{Öffentlichkeit}},
    publisher = {Doe, Jane},
    author = {Doe, Jane},
    year = {1937}
}

end{filecontents*}

documentclass[
12pt
]{book} % The class file specifying the document structure

% Set the values for the bibliography
usepackage[
style=apa,
backend=biber,
isbn=false,
url=true,
doi=true,
natbib=true,
eprint=false,
hyperref=true,
backref=false,
firstinits=false
]{biblatex}

usepackage[utf8]{inputenc}
usepackage[autostyle=true]{csquotes} % Required to generate language-dependent quotes in the bibliography
usepackage{xpatch}

% Set language
DeclareLanguageMapping{american}{american-apa}

addbibresource{mybib.bib}

begin{document}

textcite{test1}

printbibliography
end{document}

moewe · Accepted Answer

The issue does not occur when one runs the MWE as is with a current version of biblatex. The issue can, however, be reproduced if one switches to the legacy chase changing method with casechange=latex2e, (which was the - unchangeable - default in older versions [<=v3.14] of biblatex).
documentclass{article}
usepackage[T1]{fontenc}
usepackage[autostyle=true]{csquotes}
usepackage[backend=biber, style=apa, casechanger=latex2e]{biblatex}

begin{filecontents*}{jobname.bib}
@book{test1,
  author    = {Doe, Jane},
  title     = {{Öffentlichkeit}},
  year      = {1937},
  publisher = {Pub & Co.},
  address   = {City},
}
end{filecontents*}
addbibresource{jobname.bib}
begin{document}
textcite{test1}

printbibliography
end{document}

It is related to the problems with the case changer discussed in https://github.com/plk/biblatex/issues/459.
A workaround would be to brace only the first letter of the word and not the entire word
@book{test1,
  author    = {Doe, Jane},
  title     = {{Ö}ffentlichkeit},
  year      = {1937},
  publisher = {Pub & Co.},
  address   = {City},
}

With German titles it would in general be preferable to mark the titles up as German to avoid any case changing completely
@book{test1,
  author    = {Doe, Jane},
  title     = {Öffentlichkeit},
  year      = {1937},
  publisher = {Pub & Co.},
  address   = {City},
  langid    = {ngerman},
}

From version 3.15 (2020-08-16) onwards, biblatex uses expl3 case changing functions (if the LaTeX kernel is sufficiently modern and the document is encoded in UTF-8). Those case changing functions are in general more robust and do not have this issue. Update your TeX distribution if possible.

Biblatex biblography prints all caps letters when using UTF8 special characters

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