Case 4: Everything is working right but you're misinterpreting the symptoms.
Low selenium due to mercury or other metals. Though selenium binds tightest to Hg iirc.
Could be toxic and or ionized selenium floating around, and then whenever you put selenium in it just gets sucked into the mercury black hole.
Also some of the detox symptoms I'm seeing with Iodine I suspect are it bouncing heavy metals around or forming weak bonds due its extreme reactivity. This isn't necessarily a bad thing but just food for thought.
Why not have hair tests as part of the Iodine unofficial protocol to see what's going on instead of guessing - especially for the outliers who are not responding well. I'm placing money down that we will see a lot of them are extremely heavy metal toxic retention toxicity candidates.
How do these people react to sulfur? Any correlation between sulfur reactions and difficult Iodine detox?
Something stuck in throat is one of the gallstone symptoms as well. Tie ins: sulfur problems, heavy metals, lack of bile flow, iodine stirring up junk and liver is clogged so there is no exit route.