Every purchase on StubHub is covered by their FanProtect Guarantee where they certainly want to help and ensure you're attending your event. Issues are rare to happen when you buy from stubhub but they have you covered if there were any.
Being that Stubhub is a marketplace, they are not able to fully review tickets but do have tons of reviews in place that go into ensuring their fans are having a good time. If you have issues, you are more than welcome to reach back out to the StubHub Community. Just send a private message to a moderator if you do and they will gladly assist.