[KevinH]

I just tried to recreate the crash with the Alice in Wonderland public domain epub that has 3 different css files in it.

I did a Search Mode "Normal", "All CSS Files", and searched for the string "div" and it all worked just fine. No crashes at all and it found every css selector that had the term div in it. Tried again by searching for "div." to test escaping and again it all worked just fine.

So this is something specific to the epub being used or the search term.

What is really strange is that even "Normal" searches are done using regular expressions but the search term is first escaped so the search engine finds only that term as written.

I can not see why or how Normal mode would cause a crash when Regex mode does not unless the escaping of the search term somehow is causing an issue or it has something to do with the epub itself.

So we really need to have that epub and the exact search term to recreate what you are seeing and get it fixed.

Please see my earlier post about the Borkify plugin if needed.