This only happens, to my knowledge, in the CMS editing environment. A multi-reference field in a CMS collection shows the items from another collection that includes words with accents, but it substitutes those characters in the multi-select field case.

For instance: it will show a (referenced) CMS entry named "Málaga" like "Malaga". However, when the field is called in a CMS page it appears fine, as it was written.

The problem is, each time you see a referenced field misspelled you have to double check that the original referenced field is correctly spelled because of this bug.

Thank you