Problem
Long story short, I was having trouble with some keyboard shortcuts within all applications.
When I press the Alt and the Shift keys together, they don't perform the expected action.
Searching for the cause
I opened the gnome-settings -> Keyboard to see how these keys were behaving in the View keyboard layout.
For my surprise both work separately, but not together. 
Solution
After digging deeper in the shortcuts set for my keyboard, I found in the gnome-tweaks -> Keyboard & Mouse -> Additional Layout Options -> Switching to another layout I found that the Alt + Shift changes the keyboard layout by default.
And voilà , problem solved.
Why do you create a topic when you know the solution to your problem?
I'm glad you asked.
In the process to find the solution to my problem, I found this topic, where the issue unfortunately has not been resolved.
After finding the solution, I thought it would be good to write it somewhere and this seems to be a good place to do it.