I don't own the Ball/Cock toilet part but a Disk shaped-water keep running slow & steady-most potential mete out?
Answers: No matter the design of the internal hardware within the holding tank, it's purpose is to maintain water to flush the bowl.
It would appear that the VENT/ Drain Hole from the tank to the bowl isn't seal.
Another issue might be that the hardward is mis-adjusted, allowing water to take to a higher even than the top of the up/vent pipe.
Toilet hardware is one of the least expensive, easiest DIY fixes within a house.
Just my two "sense"
I had to replace mine..it be due to the minerals in the marine had stopped it up internally and amazingly little water be getting by the obstruction..You can get hold of a whole tentative kit for around 7.00 at home depot, lowes etc.