We've had an Issue with our Roland XR-640 for a while now, where the machine randomly stops, saying that the front cover is open even though it is not. A light pressure on the cover fixed the issue for a few hours before it happened again. However, it's been getting worse and worse. Today, it happened and there was no fixing it, I left the cover open and pressed the metal clip with the tip of a pen until I heard the click when it makes contact, and nothing, as though the sensor doesn't work anymore. We had to turn the machine off and on again for it to work. Anyone knows what is causing this issue exactly? Might be a faulty sensor that needs to be replaced, could be something else. Please advise.