If your camera is not taking pictures in the Connectionless mode it is likely that you have the SD card write speed set too fast in your settings. Slowing it down will slow the aircraft down and take the data at the correct speed such that your SD card can keep up with it. Since the imaging is 100% on the aircraft side in the linear missions if you have that set wrong it won't take pictures at all.
Also, make sure there is sufficient room on the SD card. We recommend doing every separate flight or small group of flights on a freshly formatted SD card.