You are not landing on edge of the block but actualy inside of block and maybe take suffocation damage .. i made same thing but with 3x3 slimeblock platform and only one pistion pushing it up and jumped in middle of 3x3 platform and take damage AFTER firts jump (so second jump will get you damage) .. sometimes u will get stuck in slimeblock (not takeing damage)
YT Video: https://www.youtube.com/watch?v=iEWEwKudnUA
MC-163957
You are not landing on edge of the block but actualy inside of block and maybe take suffocation damage .. i made same thing but with 3x3 slimeblock platform and only one pistion pushing it up and jumped in middle of 3x3 platform and take damage AFTER firts jump (so second jump will get you damage) .. sometimes u will get stuck in slimeblock (not takeing damage)
YT Video: https://www.youtube.com/watch?v=iEWEwKudnUA
1.8.1 pre3 - not fixed and here is video of me repeating bug few times :
https://www.youtube.com/watch?v=hRFDQVtfakY&feature=youtu.be