audio and video stop working after a couple of hours
I have a 2017 iMac, 4.2 Ghz, 64GB RAM, i7, Radeon Pro 580 (8GB). Presently running on Mojave 10.14.6.
For the last couple of months, and getting progressively worse, the audio and video simply stop functioning after the computer has been running for an hour or two. iTunes, Spotify, etc. etc. just don't launch when you click on a track to play it. YouTube, or any other video, just sits and looks at me with the rotating arrow, and nothing happens.
The only cure is a restart, in which case the problem just recurs again after an hour or two.
Interestingly, though, if I play a track I've recorded in Adobe Audition (or any of those), it will play quite happily. I record a radio programme and a podcast, and especially with regard to the radio programme, this is causing havoc. I can't record a full two-hour programme, because the playout software (Radiologik DJ Pro) will stop playing tracks out into the USB mixer long before two hours is up.
I have tried all the obvious things (reset SMC, NVRAM, PRAM, using different playout software, etc.), to no avail. I might mention that the system has worked perfectly as presently configured (Yamaha MG10XUF USB mixer, Radiologik DJ, etc.etc.) has always worked flawlessly. If there is any possible connected event, it may be that this problem has only existed in the last three iterations of Mojave, i.e. 10.14.4, 10.14.5 and 10.14.6.
I've been to the iStore/Apple Store or whatever it's called here in Frankfurt, Germany, where they just stood and shrugged at each other and suggested I call Apple Service, which I did, again to no avail.
I'm really in a sweat here, and in danger of losing the radio programme. Any/all help and advice would be appreciated.