Your camera or capture card has “latency” which MixCast can compensate for by resyncing the digital and input layers. First, open the Compositing (Input Device in 2.3.0+) section in the MixCast Configuration app. You can then experiment with the value of the Game Delay field ("Delay Compensation" in 2.3.0+), hitting Enter after typing in a value, to find one that causes your hands and controllers to move in sync.

Once Buffered mode is enabled, you can adjust this value in keyboard in the application using the MixCast SDK while MixCast is active by pressing the [ key to decrease the delay of the virtual world, and the ] key to increase it.