Hello,
I am not sure which DAQ board you are using, but some DAQ boards do not have Analog Output FIFO (On board memory).
If this is the case, your CPU has to handle the update of the analog output channel from the data in the Analog output buffer. If the CPU is unable to keep up with your given update rate the waveform generation will stop and you may receive an error.
If your board has on board FIFO, make sure your analog output buffer is 2xFIFO size.
On most boards with Analog Output FIFO, the FIFO size is 2048 so your buffer should be at least 4096 updates