Build 37

Thought it went well but after a while the cti gets stuck on timeline but continues to play in the Program monitor.

CTI in effect controls runs normal.

23.5.15 playback is back to normal.

Hardly ever use Render audio as they dont need rendering.

Or do I hardly ever render video as I make sure I only use gpu effects.

Are you rendering the audio of these clips via "Sequence>Render Audio..." command?  Or any of the "Sequence>Render..." commands? 

Hope this is sufficient info as of tomorrow I will be off to Aruba for some sun, sea and sand.

@Ann Bens "speaking of audio it looks like sequences with no audio (empty audio tracks) run flawless".
This is strange.  I'd like to help figure this out.  
Could you post a screen shot of your Prefs>Audio Hardware... and Prefs>Playback...?

I dont see any difference in playback with High Quality playback on or off.

I'm glad it's running better but it seems like there may still be some residual issues with performance. We did make some changes to the way ProRes playback is handled starting in 23.3 and I wonder if they are affecting this at all. Could you take a look and see if the High Quality Playback option is enabled in the Monitor and, if so, disable it? Does doing so improve playback at all for you? And does re-enabling it bring back performance issues? 

Now on build 41: speaking of audio it looks like sequences with no audio (empty audio tracks) run flawless.

@Ann Bens Ok, thanks for the confirmation.