Hey there.
The recent improvement to save game behavior (create a tmp save beforehand and check its integrity) leads to the problem, that COI doesnt have the permission to delete such tmp file on Mac. (At least thats my understanding of the error message.) I have attached a screenshot of the error message, 'Copy to Clipboard' doesnt work for me.
You can create and set permissions on a tmp file manually to resolve this issue. (see below). You have to do this for every save, however, as the .tmp file is deleted after a successful save process.
Workaround:
- disable autosaves (to avoid error messages)
- touch <save name>.tmp.save
- chmod 755 <save name>.tmp.save

I'm playing COI over Steam which runs in a Whisky Bottle, btw. Havent had any major issues so far.