On a OS X 10.10.5 system, my ExtFS (v 9.7.109) partition cannot be unmounted, unless forced. When the unmount fails, the following shows up in the system log: 9/18/15 12:23:27.532 Disk Utility: Unmount of disk0s3 blocked by dissenter PID=0 (unknown) status=0x0000c010 log=unknown message=(null) I'm not sure when it stopped working. I do not think it is the first time I've tried it since the 10.10.5, but I can't be sure. I've tried uninstall/reinstall of ExtFS, but no effect. It becomes an issue when I use VMware Fusion to run the partition in a VM. Fusion used to be able to unmount the volume automatically so it could use the partition directly, remounting it when done, but not anymore. I also have a NTFS WIndows partition that I use as a VM, also usually mounted with Paragon NTFS for OS X (v. 12.2.213), and that unmounts fine. Thanks for any help.