Hi... i'm tried to update the firmware on my zoom ms50g. But the cursor up and down seems malfunction. Sometimes it's okay sometimes it's not. Are there any member here who experienced similiar issues here. How can i fix this problem. When I connect the usb cable to my PC/Laptop the screen is just like a regular stomp powered by a 9v adaptor not firmware update screen. Should I open the ms50g n check the switch or i just a spray. Thnks