I actually can make a solid suggestion on this- former electronic engineering tech here. You should be able to recover the data using a cheap RaspberryPi like a 3b model with the GPIO pins and read the data, flash to a updated chip and insert back in unit. Getting a hold of the source bin to flash even better, then just start like new. Having two units, one could even compare the checksum of both units chips once read. Not saying super easy but very doable if you want to play with it.

Technically- you would look up the eprom chip specs, set the GPIO to match things like speed and voltage required and which pins to tap the data from. Most of the instructions are on the web and quite easy to follow. Hardest part is just isolating the chip and tapping into the correct pins, being handy with a soldering iron would help. Not seeing the unit itself I can’t guess if its socketed like say older PC motherboard bios roms are or hard soldered to board- if socket very easy to work with. Surprised actually if these things are prone to this that someone has not done a write up on fixing one. Lastly, if kinda confused look at reading and re-flashing pc bios chips, it would be very similar.

I want to add that normally those chips do not fail, biggest failure in electronic things like this normally occurs in the power supply area. Personally I’d look up the specs on that chip, fire up unit and ensure the voltages match the chip specs +/- tolerance (usually only a few points). Most read write commands are based on a voltage shift on a certain pin pulled high or low and corruption is rare without chip being put into a mode where it can change the values. Voltage spikes are another issue and just fry the darn things. (Sometimes you can see a crack in chip usually on bottom).