I've found this bug since version 1.16.201 but i thought it would be fixed.
What happens is that if you place sticky pistons on Y coordinate 1 or 0 and power it it functions normally but when it is unpowered, it doesnt attract the block back.
I thought all sticky pistons are wrong and i tested it on Y coordinate 3 but it still works.
I also thought it was because of bedrock or the void.
But it wasnt either. You can see what i mean in the pictures below.
• Place a sticky piston at Y coordinate 1 or 0(Note:I'm in a flat world and creative mode)
• Power the sticky piston with ANY redstone source.
• Unpower the sticky piston and you will see the block not attracting again
The sticky piston does not retract again
The sticky piston must retract the block
Pic 1 and 2: Sticky piston fully functioning on Y coordinate 3
Pic 3,4 and 5: Sticky piston not working on Y coordinate 1 and on bedrock
Puc 6,7 and 8: Sticky piston also not working on Y coordinate 1 and on quartz brick(You can use any othee blocks)