Observers won't get inactivate after being activated

I am testing my machines in MCBE 1.16.100.56 and find out that observers will keep activate if the block being observed have been changed.

Way to reproduce:

1.Place a observer on the ground.

2.Place a piston or redstone dust or anything that can be activated at the back of the observer.

3.Place a block at the face of the observer.

What should happen:

The redstone dust should be activated and then get inactivate, pistons should push out and then pull back

What actually happen:

The redstone dust keep being activated, and piston keep at the state of pushing out.

After testing I made sure that in Android Edition this bug also exist.