What you describe sounds like the pressurestat contacts have welded themselves together. How old is your Microcasa?

If it's seen daily use for six years, you've gotten your money's worth out of that pressurestat. They typically last 2-3 years, though some like yours will last much longer. The short-lived ones are typically at the limit of their maximum amperage. The Microcasa is 800W and at 220V, the pressurestat is switching a mere 3.6 amps. It may be that the contacts have welded themselves shut, or the diaphragm has hardened in the "on" position. Either way, the pressurestat is easy to replace and should last many years.