Hello onimod13,

If this is not a "mouse issue" then would you please try to press all the status keys (Shift, Ctrl, Alt) a few times to see if that helps  ?

It could be that some of the status keys have the wrong state and that Firefox sees them as still pressed.

If it doesn't make a difference, then maybe reboot the computer.

Any luck  ?

In addition to the above - probably a rhetorical question :

Have you made sure that the plus key is not stuck  ?

Neither of those things worked, i also have a new issue on top since the restart again which is that now websites scroll back to the top of the page if i scroll down.

I have also replaced batteries in mouse and keyboard as well as checked the usb dongles and made sure it works ok.

Hello I recommend uninstalling and reinstalling FireFox. If this does not work, please contact me.

onimod13 said

Neither of those things worked,

If you hadn't made it abundantly clear that this is not a "mouse issue", I would have suggested to toggle a preference on the "about:config" page. Now I'm just puzzled .....

I also have a new issue on top since the restart again which is that now websites scroll back to the top of the page if i scroll down.

I know that you ran Firefox with add-ons disabled when you were only dealing with the "Ctrl => zoom " issue, but as this a new problem, let's try Firefox in Safe Mode, to see if maybe one of your extensions could be causing this behavior :

If Firefox is not running : Hold down the Shift key when starting Firefox.

If Firefox is running : 3-bar menu => ' ? ' (at the bottom of the dropdown) => 'Restart with Add-ons disabled'. Then OK the restart. A small dialog should appear. Click 'Start in Safe Mode' ( not 'Refresh' !)

See : https://support.mozilla.org/en-US/kb/troubleshoot-firefox-issues-using-safe-mode