What would cause a hopper to remain full when it has many empty hoppers downstream of it? There is no redstone active near the hopper, it's not activated to OFF state.
That lever looks like it is up to no good. I know you said there is no redstone on it, but it is worth a try.
As JK said, if that Lever is occupying an adjacent block space the Hopper will be activated. If you have room to move it to the other side of the tracks your Hopper should work. It's on the "wrong side of the tracks", hehe.
Argh! Thanks to all that offered help. I never knew the lever "air gapped" to activate the block above