Unfortunately yes. I have this problem on my iP4 and OBD. The strange thing is, my sons don't! Wierd! The way I fixed mine is this way. If you have the Black plastic all you need to do is take an exact knife and cut out the protective film at the Prox Sensor. It's the big oval hole at the top of the OBD plastic case. That worked for me. Now if you have an OBD with White plastic shell you will need to do one more thing. Take a Black permanent marker and "black out" the inner portion of the Prox Sensor hole. You have to be patient but it worked for me. I am sporting a Black silicon with White plastic OBD. Hope this DIY helps!
EDIT: Just found this out with my Daughters iP4 in the Pink/White Defender. You do NOT have to cut the screen shield out from around the Prox Sensor. All you need to do is get a Black Sharpie and black out the "edges as I stated above. Don't worry about getting a little on the face of the shell. A VERY gentle scrape with a razor cleans it right up. You can not even see the black ink, but no more "face dialing"