Hello orawa,

This could be a 'mouse issue' (providing you do use a mouse) ....

Would you try this please :

Type in the address bar about:config and press Enter (promise to be careful, if asked)

Type in the search bar and look for the preference :

mousewheel.with_control.action

and set its value to 1

Then close and restart Firefox.

Any difference  ?

Solved!! Thanks.

orawa said

Solved!! Thanks.

Would you tell us how you solved it, please  ? Will be helpful to others with the same problem  !