I’m having a similar issue.
The audio seems to play back fine, but frequently the green playback wiper, the time display, and the play button freeze. When I press the rewind key command (the period on the num pad), the music will play from the start as expected (always, or almost always), but the wiper and time display remain frozen.
Sometimes the issue goes away if I toggle the display of MIDI data in a lane (i.e., change it from hidden to displayed or vice versa), but it returns soon after.
This happened with the same file on both on a 2009 Mac Pro with audio playing through a Metric Halo ULN-8 and on a 2012 MacBook Pro played through internal speakers.
Bob
Mac Pro (Early 2009)
2 x 2.26 GHz Quad-Core Intel Xeon
40 GB RAM
Mac OS X El Capitan 10.11.6
MacBook Pro (15-inch, Mid 2012)
2.6 GHz Intel Core i7
16 GB RAM
Mac OS Sierra 10.12.5
Dorico 1.1