I had to upgrade my project from Unity 2017.3 to 2017.4 because, 2017.3 terrain was crashing on a lot of mobile devices. Now, When an apk is built version code remains 1. It does not change no matter what value I set in the player settings.
Just few days ago I ended with this same problem, when I went from Unity 2017.4.2f2 to 2017.4.18f1 version.
I suspect it is a bug in Unity. You can find out more about this issue and a sort of workaround, here: