Opened files menu shows nothing instead of all opened files

Steps to reproduce:

Open C++ project. 

Open different source files.

Click on the opened files selection menu located at the top of the code editor at the left of the button used to close the current document.

The menu shows no entry.

Expected behaviour:

The menu should show all opened files and let you switch from one to another.

Frequency:

The bug occurs very frequently but not all the time. 

Impact:

On complex projects when you switch between multiple files it is very annoying and reduces the coding velocity a lot.

This bug has been introduced in version 14.0.1, I didn't notice it with 14.0.0.

More information:

The problem occurs when Qt Creator is opened on my external display. When I move the window on the laptop display I can see the menu but it is not at the right place, a little below. If I put the window back on the external display, the menu does not show.