hey winter,
to solve this error the file is needed (if the winsxs cleanup is not used)
Windows\fveupdate.exe
but after using the winsxs cleanup it can be removed without causeing an error during the installation
while looking at the files that are removed by winreducer i found some more that are left:
del /q /f Windows\System32\fveRecover.dll
del /q /f Windows\System32\de-DE\fverecover.dll.mui
REM ========== Microsoft-Windows-SecureStartup-Basic-Package
del /q /f Windows\servicing\Packages\Microsoft-Windows-SecureStartup-Basic-Package~31bf3856ad364e35~amd64~~6.1.7600.16385.cat
del /q /f Windows\servicing\Packages\Microsoft-Windows-SecureStartup-Basic-Package~31bf3856ad364e35~amd64~~6.1.7600.16385.mum
del /q /f Windows\servicing\Packages\Microsoft-Windows-SecureStartup-Basic-Package~31bf3856ad364e35~amd64~~6.1.7601.17514.cat
del /q /f Windows\servicing\Packages\Microsoft-Windows-SecureStartup-Basic-Package~31bf3856ad364e35~amd64~~6.1.7601.17514.mum
del /q /f Windows\servicing\Packages\Microsoft-Windows-SecureStartup-Basic-Package~31bf3856ad364e35~amd64~de-DE~6.1.7601.17514.cat
del /q /f Windows\servicing\Packages\Microsoft-Windows-SecureStartup-Basic-Package~31bf3856ad364e35~amd64~de-DE~6.1.7601.17514.mum
del /q /f Windows\servicing\Packages\Microsoft-Windows-SecureStartup-Basic-Package~31bf3856ad364e35~amd64~en-US~6.1.7600.16385.cat
del /q /f Windows\servicing\Packages\Microsoft-Windows-SecureStartup-Basic-Package~31bf3856ad364e35~amd64~en-US~6.1.7600.16385.mum
del /q /f Windows\servicing\Packages\Microsoft-Windows-SecureStartup-Basic-Package~31bf3856ad364e35~amd64~en-US~6.1.7601.17514.cat
del /q /f Windows\servicing\Packages\Microsoft-Windows-SecureStartup-Basic-Package~31bf3856ad364e35~amd64~en-US~6.1.7601.17514.mum
REM ========== Microsoft-Windows-SecureStartup-Package
del /q /f Windows\servicing\Packages\Microsoft-Windows-SecureStartup-Package~31bf3856ad364e35~amd64~~6.1.7600.16385.cat
del /q /f Windows\servicing\Packages\Microsoft-Windows-SecureStartup-Package~31bf3856ad364e35~amd64~~6.1.7600.16385.mum
del /q /f Windows\servicing\Packages\Microsoft-Windows-SecureStartup-Package~31bf3856ad364e35~amd64~~6.1.7601.17514.cat
del /q /f Windows\servicing\Packages\Microsoft-Windows-SecureStartup-Package~31bf3856ad364e35~amd64~~6.1.7601.17514.mum
del /q /f Windows\servicing\Packages\Microsoft-Windows-SecureStartup-Package~31bf3856ad364e35~amd64~de-DE~6.1.7601.17514.cat
del /q /f Windows\servicing\Packages\Microsoft-Windows-SecureStartup-Package~31bf3856ad364e35~amd64~de-DE~6.1.7601.17514.mum
del /q /f Windows\servicing\Packages\Microsoft-Windows-SecureStartup-Package~31bf3856ad364e35~amd64~en-US~6.1.7600.16385.cat
del /q /f Windows\servicing\Packages\Microsoft-Windows-SecureStartup-Package~31bf3856ad364e35~amd64~en-US~6.1.7600.16385.mum
del /q /f Windows\servicing\Packages\Microsoft-Windows-SecureStartup-Package~31bf3856ad364e35~amd64~en-US~6.1.7601.17514.cat
del /q /f Windows\servicing\Packages\Microsoft-Windows-SecureStartup-Package~31bf3856ad364e35~amd64~en-US~6.1.7601.17514.mum
REM ========== Microsoft-Windows-SecureStartup-Basic-Package
del /q /f Windows\System32\catroot\{F750E6C3-38EE-11D1-85E5-00C04FC295EE}\Microsoft-Windows-SecureStartup-Basic-Package~31bf3856ad364e35~amd64~~6.1.7600.16385.cat
del /q /f Windows\System32\catroot\{F750E6C3-38EE-11D1-85E5-00C04FC295EE}\Microsoft-Windows-SecureStartup-Basic-Package~31bf3856ad364e35~amd64~de-DE~6.1.7601.17514.cat
del /q /f Windows\System32\catroot\{F750E6C3-38EE-11D1-85E5-00C04FC295EE}\Microsoft-Windows-SecureStartup-Basic-Package~31bf3856ad364e35~amd64~en-US~6.1.7600.16385.cat
REM ========== Microsoft-Windows-SecureStartup-Package
del /q /f Windows\System32\catroot\{F750E6C3-38EE-11D1-85E5-00C04FC295EE}\Microsoft-Windows-SecureStartup-Package~31bf3856ad364e35~amd64~~6.1.7600.16385.cat
del /q /f Windows\System32\catroot\{F750E6C3-38EE-11D1-85E5-00C04FC295EE}\Microsoft-Windows-SecureStartup-Package~31bf3856ad364e35~amd64~de-DE~6.1.7601.17514.cat
del /q /f Windows\System32\catroot\{F750E6C3-38EE-11D1-85E5-00C04FC295EE}\Microsoft-Windows-SecureStartup-Package~31bf3856ad364e35~amd64~en-US~6.1.7600.16385.cat
EDIT:
so the fveupdate.exe should only be removed if bitlocker service is removed AND the winsxs cleanup is selected