An insider sold TransDigm Group shares recently, but they didn't buy any. Zooming out, the longer term picture doesn't give us much comfort. On the plus side, TransDigm Group makes money, and is growing profits. It is good to see high insider ownership, but the insider selling leaves us cautious. So these insider transactions can help us build a thesis about the stock, but it's also worthwhile knowing the risks facing this company. Every company has risks, and we've spotted 3 warning signs for TransDigm Group (of which 2 shouldn't be ignored!) you should know about.