Hello,
Do you use cache plugin CDN or server cache? Try to clear all cache and check then.
Do you use WPBakery of Elementor? Do you use Multiple headers?
Theme Options > Speed Optimization > Menu Dropdown Ajax Loading, Menu Cache, Static Blocks Cache > Off, clear cache of browser, and check the result. Activate mentioned options once all changes to the header/menu will be done.
Please provide URL and temporary wp-admin access, so we can take a closer look.
Regards