This is such an incredibly specific bug that i am probably the only one being affected by it, but it did manage to break my water based computer... Basically, when an armor stand if moved by water off a wooden pressure plate and back onto it in just the right timing then any sticky pistons with more than one slime block attached does not activate.

What I expected to happen was...:
The piston should activate

What actually happened was...:
The piston did not activate despite a powered pressure plate with an armor stand on top of it being right next to it. it does not happen if the piston only has one or no blocks in front of it

in the google drive folder below i put a video that shows the exact issue in vanilla 1.20.4. the setup is too complex to describe in worlds. usually you have to try it a few times because the timing is very specific. i got lucky in the test and it happened first try:
https://drive.google.com/file/d/15qo50M1ZfXAu47U9q23uKpGLBc781ExB/view?usp=drive_link