Something weird happened yesterday (I work with Cubase Pro 11 on a powerful iMac Catalina). Normally a 10 min piece takes let’s say 10 min for audio mix down, and you can see the progress in the mixdown window. But suddenly out of the blue, with all the same settings as always, this happens:
mixdown window appears, but no file information and no blue progress line. Like the mixdown-process wants to start but don’t start
mixdown is happening though (you can see movement on EQ plugins and controllers), but it takes 1 full hour for this 10 min piece.
UPDATE (PARTLY SOLVED)
Very weird (and I’m using Cubase already for 30 years):
I tested mixdown with my 5 most recent project (all the same template settings/bus settings/ etc).
2 work fine; 3 did not
the 3 that were not working, I could mixdown separate tracks or separate busses without any problem. Except the master mixdown did not work
there is only one plugin on my master bus in my template: TC Electronic Clarity. I realized that the plugin was on, but the Clarity-hardware was not. Turning on the hardware, and mixdown was fixed! Also: removing this plugin from the master bus and mixdown was fixed.
but very weird: the 2 project without problems, did a correct mixdown, even with this Clarity plugin active and the hardware Clarity turn-off…
Well there is a more circuitous route when processing an offboard processor and I have not seen such delays with UAD. The OP has said that it came out of the blue, so presumably he had not added anything new to the mix?
if I just add a UAD plugin to my project, the latency is 10 times higher then all other plugins. In stead of for instance 4ms latency for a normal ‘powerful’ plugin, with UAD it will be 400ms.
but: if you click the small mic-button on the left down side of the UAD plugin, all is fine and latency drops to normal level (what this does is sending the plugin directly to the DSP of the Apollo hardware and not some kind of delay compensation to Cubase)