Pistons are not working at Y level 1

This piston does not retract the slime block at Y level 1 (i checked for connected blocks, but there are no) (I was playing in a world with a friend) Video: https://1drv.ms/v/s!AitQ1Noc9ii72y3Haym_6fm_A1yl?e=0jZWSl

Steps to Reproduce:

    1. Create a flat world in creative mode

    2. Break the blocks a bit, that the  piston cannot push them

    3. Break the bedrock

    4. Place a piston with a slime block on top at Y level 1

    5.  Place a leaver and flick it

Observed Results:

The Piston pushes the slime block, but when you retrack it, the piston cannot pull the slime block.

Expected Results:

The Piston retracts the slime block.

Video: https://1drv.ms/v/s!AitQ1Noc9ii72y3Haym_6fm_A1yl?e=0jZWSl