Wither stops dropping blocks when breaking them.

I have a cobblestone maker that uses a wither that mines the stone and then gets collected. The wither gets damaged by a snowball from a snow golem inside an obsidian cage and because of that breaks the stone above him. At first the blocks drop but after about 2 seconds the blocks carrt on getting destroyed but stop dropping as an item. I have noticed this on minecraft on my phone and switch even before the 1.18 update.

Below is what I am using. Also this is done on easy mode. The stone that is generated on top of the wither cage are the ones getting broken.