Edit 2020-07-14: This problem is now also reported as issue #587 on MiKTeX’s repository on GitHub.

Remark: As of 2020-07-13, the problem occurs only for the pre-release MiKTeX distribution, so only beta packages are affected.

The following example:

MWE 1:

documentclass{article}

%usepackage[swashQ]{fbb} % No error.
%usepackage{ETbb} % No error.
usepackage[swashQ]{ETbb} % Error when using with textit{…}.

begin{document}
    Quest. % No error.
    textit{Test}. % Error when using with usepackage[swashQ]{ETbb}.
end{document}

fails with error Sorry, but pdflatex.exe did not succeed. The log file hopefully contains the information to get MiKTeX going again: C:Users⟨User⟩AppDataLocalMiKTeX2.9miktexlogpdflatex.log and the contents of the mentioned log are:

⟨time⟩ INFO  pdflatex - this process (2904) started by 'texstudio' with command line: pdflatex.exe -synctex=1 -interaction=nonstopmode texstudio_JeXOrj.tex
⟨time⟩ INFO  pdflatex - allowing known shell commands
⟨time⟩ INFO  pdflatex - enabling input (output) from (to) processes
⟨time⟩ FATAL pdflatex.core - Read operation failed.
⟨time⟩ FATAL pdflatex.core - Data: path="", read="0", n="1"
⟨time⟩ FATAL pdflatex.core - Source: LibrariesMiKTeXTeXAndFriendsincludemiktex/C4P/C4P.h:255
⟨time⟩ FATAL pdflatex - Read operation failed.
⟨time⟩ FATAL pdflatex - Info: path="", read="0", n="1"
⟨time⟩ FATAL pdflatex - Source: LibrariesMiKTeXTeXAndFriendsincludemiktex/C4P/C4P.h
⟨time⟩ FATAL pdflatex - Line: 255
⟨time⟩ INFO  pdflatex - this process (2904) finishes with exit code 1
⟨time⟩ WARN  miktex.core - still open: texstudio_JeXOrj.tex
⟨time⟩ WARN  miktex.core - still open: texstudio_JeXOrj.pdf
⟨time⟩ WARN  miktex.core - still open: texstudio_JeXOrj.aux
⟨time⟩ WARN  miktex.core - still open: texstudio_JeXOrj.log
⟨time⟩ WARN  miktex.core - still open: "C:Users⟨User⟩AppDataLocalProgramsMiKTeX 2.9fonts/vf/public/etbbETbb-Italic-tlf-swash-t1.vf"
⟨time⟩ INFO  pdflatex - this process (23036) started by 'texstudio' with command line: pdflatex.exe -synctex=1 -interaction=nonstopmode texstudio_JeXOrj.tex
⟨time⟩ INFO  pdflatex - allowing known shell commands
⟨time⟩ INFO  pdflatex - enabling input (output) from (to) processes
⟨time⟩ FATAL pdflatex.core - Read operation failed.
⟨time⟩ FATAL pdflatex.core - Data: path="", read="0", n="1"
⟨time⟩ FATAL pdflatex.core - Source: LibrariesMiKTeXTeXAndFriendsincludemiktex/C4P/C4P.h:255
⟨time⟩ FATAL pdflatex - Read operation failed.
⟨time⟩ FATAL pdflatex - Info: path="", read="0", n="1"
⟨time⟩ FATAL pdflatex - Source: LibrariesMiKTeXTeXAndFriendsincludemiktex/C4P/C4P.h
⟨time⟩ FATAL pdflatex - Line: 255
⟨time⟩ INFO  pdflatex - this process (23036) finishes with exit code 1
⟨time⟩ WARN  miktex.core - still open: texstudio_JeXOrj.tex
⟨time⟩ WARN  miktex.core - still open: texstudio_JeXOrj.aux
⟨time⟩ WARN  miktex.core - still open: texstudio_JeXOrj.pdf
⟨time⟩ WARN  miktex.core - still open: texstudio_JeXOrj.log
⟨time⟩ WARN  miktex.core - still open: "C:Users⟨User⟩AppDataLocalProgramsMiKTeX 2.9fonts/vf/public/etbbETbb-Italic-tlf-swash-t1.vf"

Commenting out textit{Test} as well as switching usepackage[swashQ]{ETbb} to usepackage{ETbb} or to usepackage[swashQ]{fbb} removes the problem. So there is probably a conflict between swashQ option of ETbb and some internal macros of textit. I have no ideas how to investigate this matter further, but maybe someone of TeX.SX community could help to eliminate this problem.

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Edit 2020-07-14:

A similar error occurs when using either fbb or ETbb (without any options) with footnotes supplied by footmisc package with option symbol. An illustrative MWE is below. It also works well on the stable MiKTeX and fails on thr pre-release.

MWE 2:

documentclass{article}

usepackage[symbol]{footmisc}

usepackage{fbb} % Error when using with footnote{…} of footmisc with option symbol.
%usepackage{ETbb} % Error when using with footnote{…} of footmisc with option symbol.

begin{document}
    Test% No error.
    footnote{Test.}. % Error for usepackage{fbb} or usepackage{ETbb}.
end{document}