Good idea. Start with downloading to TAG (not custom board), and download a clean - unmodified version of a simple App, like Hello Sensor or Proximity App, or some such. If you can get this to work, then move forward to next step.
If you have added a lot of code or large memory buffers, it is possible to corrupt the module every time it runs.. in this case Recovery will run successfully and the App will run one time (or maybe start to run and die).. and then the next download will fail. I have seen this and solved the problem by reducing the size of a memory buffer that I had allocated.