Korg 800DV/Maxikorg K2 Tuning Issues on both upper and lower voice 

Documenting same tuning issues with the 800DV. I believe there are not many videos on the internet demostrating the issues on the 800DV.
Here, I demonstrate some tuning issues with the 800DV.
Symptoms:
Upper Voice has tuning issues on the lower register of the keyboard while on the upper register, the tuning is stable.
Lower Voice has tuning issues on the upper register of the keyboard while on the lower register, the tuning is stable.
If anyone has any experience with this issue, do let me know in the comments below.