I have tried that (which I thought could have been the problem because I remember having that option) but it turns out to be part of the MACRO tab only. There is no "single press" or "hold the button" option when configuring the mouse, as seen in this pic: https://imgur.com/a/jvk0q

In any case, the problem would persist as it also happens when I press the ALT key on the keyboard, it is not exclusive to the mouse. Is there any option within the options of the computer to switch that repetitive pressing off? (In Windows 7 btw). Right now I have opted for removing the key from the keyboard so I do not mess up when raiding or simply dungeon-ing.

As for the mouse, I simply switched to ALT GR (which seems not to be giving me headaches) for my third tab spells and it works but the thing is that, if I try to tab out of the game into a different program, the same sh*te happens D:.

Thanks for your answers and support.