Bug or IOS problem?

I had the old version of this, I loved it so much I thought I would lay out .99 for the 3D version.
Was it a mistake?, a bug or an IOS problem? Because when I installed it the app went strait to the startup screen just like it was supposed to.
But when it loaded the main screen it opened long enough you could see what it looks like with an audio type beep for the flash of a second and back to my home screen.
I tried reinstalling and not opening it until I had rebooted my phone to no avail, I went so far as to even try a hard boot before opening and again the same problem.
My question is this, why is it with some apps like this one that some people have no problems with the app while others it becomes a crappy rating and harsh reviews because they lost .99 on an app that works for some but not others.
You would figure the developers would target this issue of why out of multiple iPhone users running the same IOS that purchased this or any other app that has this issue that they could pinpoint what is causing some users to experience problems while the others are not.
Some body out there has to know what is causing this so why dont they fix it?

Nittrobug about aSmart HUD 3D +SpeedCams, v5.1.1