Shulker boxes don't conduct redstone signals when open. However, they don't trigger redstone updates around them, causing redstone components to not react to the changed conductiveness of the shulker box.

To reproduce

In this contraption, the redstone lamps don't turn off when a shulker box is opened:

In this contraption, they do:

Video

Minecraft 1.15.2 - Singleplayer 2020-06-21 11-08-02.mp4