Lately I was having an issue in the org to html conversion where the newline characters got appended with funky unicode characters.
Full detail is in this reddit post I started.
The fix was to add the following code after the line
(funcall lang-mode) in
org-html-fontify-code defun in
(when (require 'fill-column-indicator nil 'noerror) (fci-mode -1))
Make sure you delete ox-html.elc else your patched ox-html.el won’t be effective.