Hi,
lately our website top menu and logo is showing double. In the beginning the first menu loads and then after some time a second one appears. We did not do anything to the menu. This must be some glitch.
Also, a customer noted that the login/ register link is not working, nothing happens when you click on it.
Please deactivate all the 3rd party plugins and activate only theme-required plugins on the site, and then check the issue. I am sure your issue will be solved. Then activate the 3rd party plugins one by one and check which plugin is creating the issue for you.
Otherwise, if the issue still exists, then keep the 3rd party plugins deactivated and let me know I will check and give you a possible solution.