Progress window not shown while exporting audio files.

I don’t know whether it is a system-specific issue (as I am using macOS High Sierra Golden Master at this moment).
However, everytime I try exporting audio files I couldn’t see the progress window shown but just my mouse cursor rolls as a colored ball.
(Dorico version

P.S.: Please do offer stem output so users could do their own track mixing.

Yes, this is a known issue.

Thanks. The information you forwarded to me indicated that the must-reboot issue of playback controller is not a system-version-related issue. I am gonna update my reply on the macrumors forum.