Stacks of falling anvils disappear

When the bottom of a large stack of anvils is removed some of the anvils in the stack disappear. It is notable that this does not happen if you fly and follow them up staying even with the one that is falling.

What I expected to happen:
anvil falling animations cascading upwards and one less anvil then I stacked
(as I removed one)

What actually happened:
Multiple anvils falling at once and many anvils disappearing from the stack.

Steps to reproduce:
Stack a large number of anvils (I was against a tall wall and had about 60)
Remove the bottom one
Stay still until they are done falling
Note how many are left