I was going through exporting stems for a lot of my projects, and a few of them exported all 0-byte files. One of them even exported mostly fine, but then cut to silence halfway through the second-to-last file and exported 0 bytes for the last file as well as the master mix.
I’ve experienced this before, but haven’t been able to properly reproduce it consistently. A workaround for me was to render the stems again. I think I was using firmware 1.6 at the time.