If I am powering/unpowering a sticky piston at the exact same time I am pausing/quitting the game/unloading the chunk, the piston will remain in the previous state, completely ignoring the update. This did not occur with regular pistons.
20w06a partially fixed this; it still occurs but much less common than 1.15.2-pre2 and 1.15.2

Reproduce:

    1. build an array of zeroticking machines as they provide a lot of fast updates to the piston (machines that don't use unintended behaviour, like flying machines, are affected as well but as they are slower it's harder to demonstrate the issue with them)

    2. repeatedly pause the game/reload the world (in singleplayer) or kill the server (in multiplayer). Regular saving & shutting down of a multiplayer server will not cause the issue, despite singleplayer running an integrated server.

    3. most likely some of the machines will have stopped working, with a piston being powered and not firing.

I am already sorry for most likely duplicating something... after about an hour of searching i couldnt find any similar issue though