Hi Lamiaa,
A good topic to start a discussion. The main consequence is the failure of that product in market.Here i would like to give some examples recently happened though they are not related to medical devices but i think they are suitable to the topic and they all are the results of insufficient design control.

First one is Samsung Note 7 failure because of explosion problem. I read somewhere that the Lithium battery comes with the sheets which separate the +ve and -ve sides of battery. In Note 7’s battery the separation sheet layer was not too thin and if it gets heated while charging, it can be burnt away and causes the explosion.

Second case is similar and happened in 2004 with Nokia BL5c Batteries. The company went under loss and had to recall all the similar products from market as Samsung did now with Note 7.

Third example is from automobile industry, where Hyundai Motors recall all their Elentra Model (Not sure exactly) from market as there was some engine noise problem in new cars.

I hope you get some idea that what happens if there is insufficient design control.