Griffon adventures starting area bug

If I'm standing at the flag to start a griffon adventure, whether I'm on a griffon or not, I get the "you must be on a griffon mount in order to attempt this adventure". If I'm not on a griffon and I mount one, I get the same message after mounting. In neither case will the adventure dialog pop up to let me start. I have to move well out of the starting area and back in, while mounted, to get the dialog to pop, and sometimes it pops up and disappears immediately, and I have to do it again. In the case of the Desolation Expert one, it means moving completely off the platform and jumping/flying back in. In addition to the Desolation Expert one, I'm seeing the same behavior at the Desert Highlands Master and Domain of Vabbi Master courses, so I assume this is true for all such adventures.
I suppose it's a minor bug since there is a workaround, but it is definitely new since the patch on the 23rd.