Yamaha HTR-6065 Receiver ‘Internal Error’, ‘Error 4000’, No Model Info Full Repair

Two complete solutions on how to fix the “Internal Error”/ or “Error 4000” and “No Model” Info error messages on various Yamaha Receivers. This works with at least the following Yamaha home theatre receiver models:
RX-V673
RX-A773
RX-A720
RX-A820
HTR-6065
HTR-7065 (probably)
HTR-6067
Always work with power DISCONNECTED. Do this accepting the risk and understanding you will certainly void your warranty - but the assumption is that your model is well past warranty anyway, so what have you got to lose? Life without risk is dull and pointless. My HTR-6065 is from 2012, so a decade out of warranty.
Link to the current Yamaha firmware: au.yamaha.com/...
Tools needed:
Empty USB drive - if firmware update method works
Philips head screw driver
Magnifying glasses or bloody good eyesight
Fine-tip soldering iron
Solder and jumper lead (easier than bridging the pads with solder - which then has to be removed)