Hi, no specific experience with this issue in Phocus (never shot it tethered when I had my H3Dii-39ms but anyway), what I know to be MFDB technical support suggestion 101 (and which I have received an infinite number of times) though is, what firmware are you running? is everything up to date? I would apply this to everything possible first, I.e computer operating system, version of Phocus, and camera firmware.
Best,
BH