WKHTMLTOPDF hanging at 10% for site with authentication mechanism

Question

I am facing an issue using WKHTMLTOPDF utility for converting HTML to PDF. Utility is working fine for local files and for websites which do not require authentication but for sites with an authentication mechanism, it hangs at 10% for an infinite time and does not create output pdf at all. I am using WKHTMLTOPDF latest version 0.12.5 (with patched qt) I have already tried passing --username and --password parameter to the command. Strange part is if I do not pass --username and --password parameter, then it throws authentication error (which is expected behavior) but after passing --username and --password parameter, it just hangs infinitely. Below is my command for converting HTML to PDF:

wkhtmltopdf.exe --username "USER" --password "PWD" "https://site_with_authentication" "C:\temp\test.pdf"

Questions:

1. Any solution for above? Any thoughts why it keeps hanging.
2. Any workaround to bypass authentication.
3. Any log file of wkhtmltopdf utility to debug where exactly it is hanging.