I found a workaround:
You need to equip “Chain of Exemption” necklace before riding the Pterodax, after that I still got stuck, but at least the quest was completed, and I could just fly to the quest end manually.
Edit: I guess this was a coincidence - a GM has flagged the quest as completed right at the time I was trying that strategy
finally after about three days, a game master marked it as complete for me!! i just had to go into the cave and find nisha and she had the next few quests for me 
so happy!!!
This didn’t work for me… 
This did not work for me
Just wanted to make an update from my original reply, which was that I was facing the same issues. I created a bug ticket and after 2 days the GM responded and autocompleted the quest for me. As of now I am running through Vol’dun finishing off the zone. Best of luck!
I’ve put in two tickets and both times was told just to go to Wowhead. Apparently putting in a ticket does nothing. It’s not Wowhead’s job to fix Blizzard’s bugs.
Someone in a smaller thread submitted a ticket and had it fixed. I’ve just put one in.
Unfortunately the 2 tickets I submitted do not show up in my tickets. So have submitted a ticket about my tickets for this quest not showing up!!
[Into the Dunes] stalls over the brine basin after cut scene then resets back to flight point in the Royal Armory… help
This is still bugged for me. Please just let us progress to the next quest.
Day 7 of being on this quest. I keep submitting tickets and keep getting the same response. This is getting really, really frustrating. Just give us credit for the quest.
The quest to start the Vol’dun area (into the dunes) is completely bugged out for me. Right after the cut scene ends it just holds me mid air on the pterrordax. I’ve tried reloading everything and uninstalling my addons.
I have the same problem. I have tried with other solutions but the problem continue. This mission is a stopper to unlock zandalary race.
Same. I thought maybe it was because I was trying to quest in Zandalar while still on Warlords of Draenor Chromie timeline so I went to Org to change it to BFA timeline and still bugged.
Even the alt f4 fix doesn’t even work on it anymore. I need it to unlock the race
You are not alone - same here though eventually I rubber band back to the starting point.
Tengo el mismo problema justo desde ayer dia 2 ya no puedo continuar con la mision de las Dunas, quisiera saber si alguno tiene la solucion para esto que es muy fastidioso, arregle los problemas de red, grafico, errores, ethernet, uninstal todo y sige, que tedioso de verdad
Same issue here. Nothing I’ve tried helps including previous “work around” (alt f4). Please fix. Thanks!
Ergo
I’m having this issue as well. Disabling addons, skipping the cutscene or pressing Alt+F4 during it. Edit: Ticket works! Quest advanced by Asmoranom. Thanks GM!
This sucks same issue starts the quest then get too the desert and that’s it got to restart the game won’t let me finish anything:((