DAQ Internal Error when triggering

Using the data acquisition toolbox and a NI PCIe-6323, I have a session with counter outputs and a session with digital outputs. I want to use a counter output as the clock for the digital outputs and trigger both sessions to start at the same time. Since it seems counter outputs ignore anything to do with triggers, I set up the digital outputs to just trigger on the first clock pulse. Set up as so:

%     Use the counter channels as a scan clock for the digital out channels    
addClockConnection(this.device,'External',['Dev1/' clkTerminal],'ScanClock');

%     Trigger the digital outputs off the first clock pulse    
addTriggerConnection(this.device, 'external', 'Dev1/PFI12', 'StartTrigger');
this.device.TriggersPerRun = inf;

Where this.device is a session with a set of digital outputs. Then output is started with the following, where this.deviceClock is a session with counter outputs.

 this.device.startBackground;
 this.deviceClock.startForeground;
 stop(this.device);

Occasionally I get the following error at startForeground, even though the pulse was generated successfully:

 Internal Error: Unexpected operation checkForTimeout occurred in state ReadyToStart.