OH, that's interesting!!
Please update us on how your problem gets resolved!!
I had to jump through some hoops in preparation for upgrading OS X so that I can use On1 RAW 2019......(backups and such)....
I hope to upgrade today and give it a try later this afternoon.
They are aware of the issue with export and hopefully will have a fix/patch for it with the next update. It seems to be exporting a bit better from being in browse rather than develop etc. Still slow like it was in PR2018 but working none the less. Seems to be a few other little bugs here and there but once they dial PR2019 in it's going to be quite an awesome program. Some people are not having issues at all but of course I am!!! LOL figures!