Could you share the XLMForm (extract), please.
You can check the issue by temporarily changing the calculate types to text.
An alternate form design would be to put a select_one first, second, third directly as initial questions, with triple select_one and a choice_filter to exclude the already selected item(s).
Maybe you can also try if the select_multiple from … is possible with rank. (I am afraid, not). See https://community.kobotoolbox.org/t/create-a-select-one-question-from-a-select-multiple-question/35087/7 and
https://docs.getodk.org/form-logic/#generating-select-ones-from-repeats
