Ctrl + Arrow changed behaviour
Since version 4.8 the behaviour of Ctrl + Left (and Ctrl + Right) changed.
Ctrl + Left is a standard shortcut used for moving the cursor from one word to the previous one (and Ctrl + Right to the next one in left to right writing).
It seems that in 4.8 that same shortcut is used for switching from one tab to the next one. Still Ctrl + Backspace or Ctrl + Shift + Arrow work as expected.
The standard shortcut for swithing tabs seems to be Ctrl + Tab (and Ctrl + Shift + Tab) so I propose to use them instead of Ctrl + Arrow.