Pistons, droppers, dispensers, observers, & redstone lamps become stuck in an on or off-state & act like solid/opaque blocks until world-reload
Sometimes, when you load up a world, a couple random pistons, dispensers, droppers, observers, and/or redstone lamps will be stuck in either their on or off state, and will not change state until broken, pushed, pulled, or upon reloading the world. The blocks also act as if they were just normal non-rs-component solid/opaque blocks. This means that pistons will be able to pass a redstone signal through them via dust & a repeater, and the blocks will not be affected by any redstone-component-specific bugs like MCPE-18114. This bug is difficult to reproduce since it seems to be somewhat random as to when it occurs, but it tends to happen to the same particular blocks when testing.