Currently only tested on iOS.

While using the 'Joystick & aim crosshair' control mode, no blocks can be destroyed whilst tapping on the attack/destroy button, however if the button is held down, blocks can then be destroyed. Does not affect attacking or survival mode.

To replicate:

1. Select the 'Joystick & aim crosshair' control mode.
2. Open any pre-existing world or create a new world in creative.
3. Try to destroy any blocks in the world by tapping on the attack/destroy button.

Observed Results:

The block visually appears to disappear for around a tick before being back in place. It is not a ghost block, it has a physical hitbox and collision box. Can be broken after switched to survival just like normal.

Other Important Notes:

Some vegetation seem not to be affected by this bug, e.g. grass, flowers, saplings and crops.