One of my toilets has a mansfield valve and when I flush it, it makes a loud clunk noise. Also only a little bit of water fills in the bowl below.
When I take the tank top off and view the flushing, there are 2 pieces to the valve. 1 inner piece gets pulled up when I push the handle, and the outer piece goes up with the inner piece but quickly falls down with the loud thunk noise. This stops more water from getting to the bowl.
How can I fix this? The outer valve piece dropping faster than I want it to, plus making a loud noise when it falls?

Thanks