Our DRS12A has quit reading beyond a couple of miles. We reset it and it worked for a day of so, then reverted back to just reading 2+/- miles. Have not been able to find a repair dealer for any help.
If you go to the FURUNOUSA.COM website and click on where to buy it will bring up all the dealers in your area. https://furunousa.com/en/company/find_a_dealer It does sound like it could be a magnetron issue. You can also send it in to the FURUNO service center. You would need to obtain an RMA number from the FURUNOUSA.COM website and then you would receive shipping instructions and an RMA number. https://furunousa.com/en/myaccount/returned_merchandise_authorization
If you go to the FURUNOUSA.COM website and click on where to buy it will bring up all the dealers in your area. https://furunousa.com/en/company/find_a_dealer It does sound like it could be a magnetron issue. You can also send it in to the FURUNO service center. You would need to obtain an RMA number from the FURUNOUSA.COM website and then you would receive shipping instructions and an RMA number. https://furunousa.com/en/myaccount/returned_merchandise_authorization