tracking off when controlling a machine with video adapter connected

I have a bunch of machines connected to projectors and when I try to control the machines remotely, my view of the cursor is off (usually by an inch, give or take) from where the cursor is on the users screen.

It only shows one cursor, so it gets dicey trying to click on things when you don't actually know where you're clicking.

Unplug the adapter and control is back to normal.

Any idea what could be causing this?

ARD 3.8

remote OS 10.9.5

local OS 10.10.3 (been happening before upgrade as well)