If you put out a water source in a flat area and an observer next to it, every time the water's state is changed it outputs a redstone signal causing it to flash out signals which did not occur in 1.13.

Steps to replicate:
Place a water source on a flat area
put an observer next to the water source so it's able to observe the water source
remove the water source with a bucket and watch the observer output multiple redstone signals.
I originally encountered this when i was creating a creeper farm which relies on getting a redstone signal from observing water, but the design seems to break in 1.14 thanks to this. Is this a bug or a feature? If you stack this like in the photo attached it will randomly choose how many redstone ticks will output.