The markdown files Anytype exports have really long (encrypted) names. It’s worse with exported files, which have those long encrypted characters + the original file name. For example, if you append a .pdf document called example_pdf_document.pdf, when exported the file would be renamed to something like baytueidwdlhklg4udngkq4oygdupkk2evi8834dhqyzjye42r5plb7uk5y_example_pdf_document.pdf which is really long and perhaps that poses a problem to macOS.