Indd 16.0 x64, and the previous version. Windows 10. Create a document with test and also linked Indesign "sub-documents" in it. Run spell-check or find & replace, set to check all open documents. Indd opens the linked document, then freezes. You cannot save, quit, or anything. I have submitted numerous crash reports. See https://community.adobe.com/t5/indesign/indesign-2020-crashes-while-using-spell-check-with-linked-indesign-files-on-windows-10/m-p/11608010?page=1#M404257 for details.

My documents are typically books with 10-20 indesign files in each book. Some of the indesign files have placed (linked) indesign files, typically standard "boilerplate" that must be the same everywhere. When I run a spell check across all of the open docs in a book, it opens the linked file then freezes. I later discovered that it does this on a single document if it has placed indd files and you tell it to search all documents.