Reply To: Sticky header sporadically doesn't work on Firefox

Hello,

Please deactivate all the plugins except these ones:

Contact Form 7
Mailchimp for WordPress
Safe SVG
Slider Revolution
WooCommerce
WPBakery Page Builder
XTEMOS Post Types plugin

If the problem has gone, activate the plugins one by one, checking the issue to detect which one causes the problem.

I am checking on my testing site, the sticky header works properly in the Fire Fox. If you have the child theme, check that issue in the parent theme.

Best Regards