use a spritz of deoxit. do not use wd-40.

a small amount of bee's wax in the right place will probably fix it as well.

P.P.S. Are you sure that your switch is really broken, or does it just need a good cleaning with DeoxIT?

https://www.amazon.com/Hosa-D5S-6-DeoxIT-Contact-Cleaner/dp/B00006LVEU/

Maybe Canada has some regulation about the chemicals in Deoxit? Here's the US version:

https://www.amazon.com/Hosa-D5S-6-DeoxIT-Contact-Cleaner/dp/B00006LVEU

I was able to solve this by removing the tubes and using DeoxIT on the pins. Careful not to get any on the glass; it will remove the ink markings. Some fine sandpaper on the pins might help, as well.

first step is Deoxit. Take the case off and clean all the pots and switches.

deoxit. all the knobs, sliders, switches, etc.

clean out the inside of the machine. use a paintbrush / toothbrush to get the dust that has settled close to the boards. be gentle, take your time.

while you're digging into those two things, hopefully you'll get a better look at the caps, or if anything is notably burnt. that hiss could be a few different things, but luckily there isn't too much complexity inside there.

that's a great unit, i wish you the best of luck.

Thank you!

But I prefer not to disassemble it because I want to keep it on the original condition.

So you said you recommend a Alcohol or dripping contact cleaner or maybe even Nail polish remover wipes? (Like this one for example?)

Because the mouse is quite new but I didn't use it a lot so maybe it gained some stickiness.

Deoxit spray.