I have the exact same specs and have run into the same issue which has made me have to downgrade to 3.6 in order to use PHP 7.
What I found to be the issue is a missing PHP 7.1 folder on installation. My troubleshooting of reinstalling and uninstalling has shown that the issue only occurs:
1. PHP 7 will run smoothly but will not actually be working since I received an error about not choosing curl when it was listed as selected in the menu. this goes back to my suggestion of this issue being related to PHP 7 folder issues.
2. PHP 7.2 being selected as a version leads to total death of Apache which then leads t the programme not working after such an event leading to only a reinstallation to fix.
Hope this helps to address this problem. Until the issues are removed, I will safely stick with version 3.6.