Selecting 'Prominent' for Haptic Alerts disable Haptic Alerts on iPhone

I'm trying to choose the "Prominent" version for Haptic Alerts. When I click on Prominent, it untoggles Haptic Alerts itself. I've restarted, checked for updates, etc...can anyone tell me why this is happening?

[Re-Titled by Moderator]

Original Title: Prominent on Haptic Alerts