[media]
Observer sometimes when pushed by piston and back not send any signal
In the video, you can see that the observer works well in the first three attempts, but in the final attempt, it does not receive any signal
And this is not always the case, sometimes it does not receive the signal the first time
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The video is difficult to follow because too many actions are taken too quickly and you have not described your expected results. However, I believe what you are seeing is a result of the pistons updating in random order, and not failure of the observers. See MCPE-16371.