I’m guessing the little metal contacts in the switch are getting stuck pressed together. You can maybe figure it out by taking the switch apart: this can be done by sliding two tiny screwdrivers or other thin pieces of metal between the switch housing top piece and the little plastic flaps from the housing bottom piece that hold the switch together. Slide your metal pieces in, pry the little flaps outward slightly, and pull up just slightly, and the spring inside the switch should do the rest. You can then visually inspect the inside of the switch, and reassemble the parts.
In some cases you might need to actually remove the little metal contact pieces to fix it, if e.g. one is bent out of shape. That would require desoldering the switch from the PCB.
In the worst case, you can solder a new switch into that spot.
If you can’t figure it out yourself or don’t have the tools to desolder/solder the switch, you might try emailing Matias support. They’re pretty friendly and helpful in my experience.
