I guess you are right! 
haha, easily done 
I have this same problem with a phantom blue border, - but it appears on the published website! Strange enough only on the first button in a menu-list with several buttons. the others are ok. How can I get rid of it?
Please have a look at it on a mobile view:
https://test2.riccardodelfino.eu
and have a look at my screenshots.
Thank you for any help or suggestions!
This is an outline for accessibility.
It depends how which component you’re using to create that menu, but the following tailwind class will remove the blue outline: outline-0
I can’t quite tell from your site which combination of components you’re using to create that menu, so if you’re not sure where to add that class, can you post a screenshot of the tree structure of the page or send me a link to your project file? 
Thank you for your reply, Ben! 
Here is a screenshot of the tree structure, I used Dropdown and Modal to create this menu (it was quite a bit of work, trying to find a way to make a bilingual site).
How could I send you the project file? Via WeTransfer, or else…???
Where and how can I insert the tailwind class you mentioned? I am a dummie with everything concerning codes and classes. 
And may I ask a second question: I can’t figure out how to make the mobile dropdown menu being fixed. Actually it is moving up and down on mobile, which is a bit confusing and annoying (please see screen-video 1 from my mobile).
This happens only on mobile device, but not when I simulate a mobile on my computer (see screen-video 2 from my computer).
Thank you very much for your help! 
(and labels are off in the editor).
