Playing in the newest snapshot and found the following bug:
Redstone contraptions that rely on activation and deactivation of pistons 2 blocks apart that face eachother with a single block inbetween (for example, the famous etho-hopper clock that has two pistons pushing a redstone block into eachother) fail to correctly sync their activation/deactivation.
In the case of the hopper clock, once the clock switches and one piston deactivates, the other should simultaneously activate. Instead it fails to push the block in front of it and gets trapped in a BUD-like state where it is powered but doesnt activate until it is updated.
The bud state result is visible in the image i added. Reproducable by replicating the shown build. In the example i have 5 blocks in one of the hoppers. After a hopper empties once, the system gets stuck.
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Replicated but there is a flaw in your design, this is not a bug. You need to use sticky pistons for both sides. Only when one pistons retracts the redstone block will the other piston realise it's powered.
That might have been it, but i'm pretty sure i tested my setup for both stick and non-sticky pistons.
However, the design seems to work again in the newer snapshots (tested in 20w20b)
I've seen this affect 1.15.2 but I'll check again to make sure.
UPDATE: I've found a way around it using observers, but can confirm the OG design no longer works in 1.15.2.