Do scripts in /usr/lib/systemd/system-sleep/ not block? I've never had one fail to complete before suspend. I had to use one last year to dump debug stats before and after sleep while we were helping debug Cezanne sleep issues.
I guess not because in my attempts to get this working I did put a script there. Does * expansion not work in these scripts? Mind sharing your script if you still have one? I have 3 tabs open to learn systemd when I have time, I did watch a video so far :)