When I replace the .htaccess file content with the one provided on the Multisite Network Setup page, I cannot login to WP admin. I get ERR_EMPTY_RESPONSE.

After I checked the Apache error log, I noticed there is Segmentation fault (11) error (segfault) for each unsuccessful login.

What could cause this issue?

UPDATE
I’ve figured out the temporary solution: I login with the default htaccess, and while I am login, I replace the htaccess content, and somehow I stay logged in. But the mystery remains.