I've got a cactus/bamboo xp farm. The cactus routes into the top of two furnaces that are adjacent. And the bamboo routes into the sides of those furnaces. Under the two furnaces are two hoppers and under those are redstone torches (attached to a lever). When the redstone torches are off, one of the hopper is enabled (checked in debug mode) and the other is disabled (as if the redstone torch was lit). When I lfip the lever, the two redstone torches light up, and the enabled hopper disables, and the other hopper that was disabled stays disabled.
The desired / expected behavior would be that both hoppers are enabled/disabled at the same time. I assume that some how either the furnace or hopper is acting as a lightly powered component and disabling the one hopper (consistently the same hopper). I can consistently reproduce this behavior, but don't understand why it's happening.
Ty @Hexalobular. I was thinking of that, because the lever is in the block space adjacent to one hopper. In the attached screenshot it's the closer hopper adjacent to the lever. However, that hopper is the one that properly responds to the redstone torch under it. The farther hopper is the one that's acting oddly.
In this image you can't see the redstone wire that connects the torches. But essentially what's happening is the lever powers the cobblestone beneath it, which connects to a wire under the oak plank. This wire splits and one goes straight into the cobblestone under the redstone torch under hopper (you can see this and the torch being off. The second branch of the wire goes further out and around (under the dirt) and connects to the torch under the farther hopper. I can affirm that the redstone torches respond correctly to the lever state, but the hopper itself doesn't.
Ok, this is definitely a bug in Minecraft. I have completely taken it apart and rebuilt it, again adjacent. And this time it's working as expected, however, debug mode reports them both as "enabled" even when they're disabled (and validated because not pulling from furnace above).
Sorry, I did have that backwards, the hopper closer to the lever is the one that's messed up. So maybe it is the lever? But it doesn't change state with the lever.
Well, it wouldn't.
When the lever is on it disables the hopper and when the lever is off the redstone torch disables the hopper.
Actually, when I copied your original setup as best as I understood it the hopper in question passed one item every time I flipped the lever off, so I'm certain that the placement of the lever was the original problem.
But I'm unable to duplicate the problem in your altered setup.