LG top washer making clanking sound only when washing / agitating

Brand: LG
Model Number: WT7800CV
Main Symptom: clanking sound
What happens & when: clanking sound when washing / agitating
Error Code (if any): NA
Parts or tests already tried: no parts replaced yet, checked the bolt under cover plate which secures washing / agitating plate inside the tub and it’s secure not loose
Spin cycle works fine
On video below you can see the tub spins freely without any abnormal noise, when engaging agitating bottom plate by hand to simulate the issue you can hear loud clanking noise. Appear to be coming from the bottom of the machine.
Photos / video link: Imgur: The magic of the Internet