We are still running v6.5.4 on Mac OSX 10.10.5 and experience this error. Our network guys say it is a Finder problem. It is a “storage access” error that may be related to the frequency with which the Finder updates its indexing. Ours happens to be network-attached storage–an EMC isilon SAN share volume with at least 86 TB free space out of 301 TB. Have a ticket into Nuendo support and hoping for relief. In the meantime, we will be updating to OSX 10.12 and move to a newer version of Nuendo but that’s as far as we can go and still be compatible with the isilon. Interestingly enough, this error doesn’t present for us with direct-attach storage like the VNX or with the internal HD.