Hello,

Setup:
I have one observer with a string between it and a block acting as a trip wire.

There are two dispensers with lava buckets connected to the dispenser via redstone.

Intended Behavior:
As skele's drop through the tube and trip the observer, the dispenser spits out lava on the first burst and then pulls it back in on the second burst.

Unexpected behavior:
When the Skele's drop too rapidly the whole circuit becomes reversed, meaning, instead of the dispenser spitting out lava  on the first burst and pulling it back in on the second burst, the lava instead stays out and when the observer is triggered, the lava is pulled in on the first burst and then spit back out on the second, resulting in the lava reaming out in between skele drops.

I've attached Screenshots and videos which should help illustrate whats going on.

I tested this using a vanilla 1.16.1 jar from the official source and was able to duplicate the bug.

Reproducing:
If you don't want to use skele's you can use yourself in creative mode and rapidly trigger the observer by flying up and down in front of it across the string.