InDesign v16.1

We have an InDesign file where the word "papier" is hyphenised by InDesign in this way "pa-pier", but after exporting in PDF, an unknown character was inserted before the hyphen and is shown as the letter "u" overlapping a displaced hyphen. Copy/pasting the word from the PDF gives this: pa�-pier

If the PDF is exported again, the problem is not reproduced.