I've been doing tests on Moby Dick and it's OK now.
The files open in Code View and the search works.
I also confirm that the exception is the file
com.apple.ibooks.display-options.xml
@DiapDealer: In addition to my own build, I also used today's deploy version. The problem mentioned
earlier is still present.
If I switch the theme from dark to light in Windows then Sigil switches (also dynamically, without closing Sigil). This works OK.
But if I have dark mode set on the system and, if only for testing, I would like to switch Sigil to light then the environment variable SIGIL_USES_DARK_MODE=0 makes such a mode "semi dark" (attached image).