In 1.15.2, when an item was either moved in or out of a container (specifically droppers/dispensers) that is in front of an observer, a redstone signal would be outputed.
However in this snapshot, the observer won't produce a redstone signal at all for moving items in and out of containers
Would you mind clarifying the reproduction steps please. When you say "moved in or out of a container", do you mean when a dropper is activated and releases an item, or is any method of removing an item able to reproduce this bug? (Hopper below the dropper, player removing item from the dropper, etc.)