Once you're not using default settings, here be dragons. In theory 802.11r is a standard. In practice enabling 802.11r puts you into the minority of users who do so. There's a lot less quality assurance coverage there.

You're at the mercy of UniFi not having any show stopping bugs (haha), the client device supporting 802.11r or at least tolerating it, and the interaction between UniFi and the client not having any show stopping bugs.