My 4 yr old daughter has been on Omnipod for about 10 months. There are two insertion problems that we have had to deal with. The first was our fault. On a small child without a lot of fat on her, you really have to pinch the skin during the actual insert so that you get a good shot in the fat. If you do not do this you get an insertion into the muscle which will bend the canula and cause problems. This was just a matter of training.
The second problem only happened once. We had the pod click but no insertion at all. It can be hard to really look in the window and see if you have a good insertion. The reality came as blood sugars sky rocketed in the night.
Other than that one time, no problems with insertion.