Bookings opened for one of the most popular walks - the Milford Track - at 9.30am on Tuesday.
There were 11,000 people logged in waiting to book but the system struggled and needed a reboot, the Department of Conservation (Doc) said.
It was fired back to life by 10.30am and the walk had sold out within 45 minutes.
The whole experience was "frustrating" and "disappointing" because it happened last year too, Federated Mountain Clubs president Megan Dimozantos said.
Doc should consider other solutions, she said.
Doc has said it was having "serious conversations" with the vendor.
"They need to be considering a new vendor. The department and the public have all lost trust in whoever's doing it right now," Dimozantos told Checkpoint.
Bookings for the Abel Tasman Coast, Rakiura, Whanganui Journey, Routeburn, Paparoa, Kepler, Heaphy, Tongariro Northern Circuit tracks will open within the next week.
Dimozantos was not holding out hope that the experience would be any better.
She said Kiwis should get "first dibs on Great Walk bookings", which would also help manage the traffic on the Doc website.
Increasing the price to match demand was not the "appropriate way" to manage traffic.
"The problem with giving a high-paying customer first dibs is that the more you charge those people, the more they expect, the more they expect, the more you give them, the more expensive it is to maintain the walks.
"I think that the way that we should be going is the opposite. We probably should be looking at a more modest experience."
Kiwis made up about 60 percent of the bookings, she said.
Job cuts in Doc was not a good move, she said.
Despite a lot of load testing the system crashed, Doc heritage and visitors director Cat Wilson said.
"I'm really disappointed that it hasn't worked because we've had assurances from the IT service provider who provides the booking system that it would work and it would be able to manage the capacity. So what we will be doing is having a very serious look at what the booking system is and how we manage it for next year and it may look quite different."
She said Doc would do a thorough review of the incident.
"We'll have to be having serious conversations about the future and what the booking system needs to look like from here on."
People who missed out should keep checking the website in case people cancelled, she said,
"People do cancel their bookings, but also have a think about when to go that are outside peak times like holidays, long weekends and the Christmas holidays and also look at some of those walks that aren't at capacity all the time. And there are plenty of those and they're also really fantastic walks."
But Doc was not looking at opening up for New Zealanders first just yet - "that's not something we've got on our radar at this point".
