Mine also seem to be due to an accumulation of stress, which can be because of sensory issues or not. Frustration from communication issues or other things, strong emotions, being yelled at, having too many things to do at once and/or not knowing how to address a task, not having enough time to myself, and probably a bunch of other things I'm not coming up with right now can all lead to meltdowns or shutdowns, in addition to sensory issues.
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Yet in my new wildness and freedom I almost welcome the bitterness of alienage. For although nepenthe has calmed me, I know always that I am an outsider; a stranger in this century and among those who are still men.
-H. P. Lovecraft, "The Outsider"