Do you have automatic hitpoint detection enabled ?
Yes
Tried using the backup function in C10 to make a fresh copy in another location?
Yes. I also tried this on my external using the " back up " function in Cubase.
Tried copying the project to an external drive?
Same as above.
Tried different preload settings in Cubase?
I’m not sure what you mean by preload settings?
Could you please elaborate?
Defragmenting the drive?
It’s a Mac and I’ve read not to do this. What’s your input on that please?
How is the memory situation when running the various DAWs?
I have 16 GB. Installed. With this project playing it has 10.11 gb free.
No backup/update or other task running in the background while testing? has happened to me 
No other tasks and I just tried with wifi off and also signed out of iCloud.
Thank you. Good questions.
PS. I just ordered an external Firewire SSD so I will test again when it arrives after July 15. Hopefully that will solve my disk overloads issues.
I guess the purpose of my thread was to find out why the other 2 daws didn’t have disk overload issues. If the new to arrive external SSD sorts it out I’ll be more than pleased