even after the recent fixes for observers this is one thing that still acts incorrectly.
i am unable to pinpoint what exactly is wrong but i do know that these setups in the image below used to act identicaly in 1.12.2. creating an upward flying machines

in new snapshorts the left one no longer works (seemingly because the pistons are pulsing too slow)

this bug breaks all doors using this type of mechanism in all locations