I am trying to book 3 award tickets to Hawaii, no easy task, I know. But I actually find space in F on a UA flight DEN-HNL.

But it errors when I book it.

Call UA and am told "The space doesn't actually exist. Oh, the flight exists, and there are plenty of revenue seats, but the (saver) award space showing on online doesn't exist." This is true for the outbound, and the return, and for the same flights on other days that are showing space online as well.

I am familiar with LH phantom award space issues, but has anyone ever seen UA's site showing UA metal phantom space?

It feels like a real bait and switch, and I am not very happy.

Is there any solution to this? Is United.com just completely unreliable even for their own metal?