SharePoint Document-ID and Chinese characters braking search

I am struggling with a strange phenomenon. We use the Document-ID on SharePoint extensively, especially for searching. So we search specifically for SharePoint Document-IDs, e.g., EMTS-1223334444-123, to find the document.

This works fine with 10 million documents, except for PDF documents with Chinese characters. I can search for phrases in the text content or other properties, and everything is found. Only the search by Document-ID does not work.