issue with YN-128 wireless shutter release

I'm having an issue with my YN-128 wireless shutter release when used in my studio setup. My setup consists of a 5DM2 on a tripod, tethered to a laptop, along with a cybersync transmitter (mounted in the hot shoe) to control 4 strobes. When I connect the YN-128, it behaves very oddly. It will only trigger a shot once in a while. I can see that the signal is actually being received (4-5 feet away) because the LED on the receiver changes color. If I press the button 10 times, maybe I'll get the thing to trigger and take a photo twice. This is never a problem when I am shooting on a tripod with nothing besides the YN-128. It's either the cybersync transmitter or tethering that is causing the issue.

Advice?

My bet would be the tethering. I use the cybersyncs and a remote trigger all the time. It is a different remote from what you have but obviously they all have the same connector and perform the same task. You have the equipment, experiment. Disconnect the tethering and see if it works then.

Well it turns out that the remote shutter release is fine. The issue is not the tethering as I suspected. It is most likely the flaky low-light focusing ability of the 5DM2 that I just learned about today.

The problem only occurs when I turned off all ambient lights so that my only light source is the modeling lamp on my one strobe. It seems that that the modeling lamp does not produce enough light (on the subject) to allow the AF to work properly.

This is the first time I learned of this issue with the 5DM2. Any suggestions on getting around this? I never had this problem with my previous body (40D) in the same home studio environment. I was shooting with my 24-70L at f/11.