I realized that the issue was caused by the mobile sticky menu being enabled in the Customize > Layout > Header section.
I have now disabled it and the problem has been resolved.
However, I would still like to have the sticky menu enabled for both mobile and desktop devices.
Since you have a relatively long menu, I would suggest using an Off-Canvas menu for mobile if you want a sticky menu on mobile without the issues you’re encountering now.
Fernando, I have enabled the off-canvas menu but it is not appearing when I try to open it on my mobile phone. Could you please take a look and see what the problem might be?