The bug is that when i tried the thing in the titile it worked in 1.14.60 but now it doesn't work anymore  ever since the nether update got released.

Steps to Reproduce:
1. Place a button on the floor and put a redstone dust in front of it with an observer in front of it. 
2. Put a Sticky Piston Facing Inwards In Front of the observer and place another observer in front of the Sticky Piston.
3. Leave a Block and place a repeater or comparator facing inwards and a piston facing upwards in front of it.

Observed Results:
The Normal Piston doesn't activate

Expected Results:
The Normal Piston Should Have Activated

For More proper proof, download the pulses-from-moving-observers world and try yourself.