Korg Poly 800 mk1 CRAZY DISPLAY

Yesterday, after a long sleep and no usage for a year, I installed new C batteries into my old Korg Poly 800 and loaded a new soundbank in via audio cable. It was working fine, but i walked away for 5 min, only to suddenly hear the keyboard sounds off an alarm sounding voice – and the following code frozen on the LED display: Program No 1.8, Parameter No: 50, Value: 01. Basically this code 1.8 50 01
No amount of resetting, taking the batteries out, waiting etc seems to clear this code and note keys are all making no sounds. No alarming anymore, just the code which always comes up. Any thoughts? I do have another “parts” specimen. It’s not working either, but if there is something to swap out? Thanks!