Welcome.
First, email Korg support to explain your problem.
Hopefully you will get a quick response.
The manual does not contain info on a reset only on performing a restore which itself requires the keyboard to fully boot up.
If needed you could try reloading the latest OS to overwrite everything, download the file and read the install instructions after you copy the expanded file onto a usb drive.
The install will be (if memory serves me correctly hence read the instruction file) press and hold Intro 1 then power up, it will then go to the files on the usb drive and you follow the on screen instructions
I do hope that you have created a Backup and a Save All file they are two separate files and it is the Save All file you will need toRestore you user data which will be erased by installing the OS.
Waiting for Korg support to respond is imo the way to go first.
When this has happened to others on another forum namely the Korg Forum the dickhead given the advice always has failed to return to update the post, hence do return and update us.