Even though “to be disconnected” sounds awkward, I think that along with its synonyms (to come off, be out, be off) are fine.
“To come off” actually makes a little more since for the things it describes, in my opinion. It refers to things that are together or secured that have kind of come apart on their own.
The first set of examples from here are good: https://dictionary.goo.ne.jp/je/60610/meaning/m0u/外れる/
If you check out words like 分ける (わける：to separate/split) 離れる (はなれる：to be separated/ apart from someone)
which literally mean to separate, the first one refers to things that you are splitting apart on your own and the second refers to being separated by distance.