Presumably then Chester did not deliberately source a second rate system from Code, and until it was properly tested by volume after re-opening, they would not have been in a position to know exactly how deficient you say it is - and by then it is too late to start from scratch...
Anyone with even a moderate level of digital marketing experience would know that once launched, the zoo's booking platform would quickly become incredibly busy. There was already a precedent for this, across many other organisations, and historically when high demand tickets go on sale. It's not a case of launching something that is untested and then falls over under load, it's a case of launching something that has been tested under load. The efficiency and positive impression alone outweigh any fees if using a third party, and there's the saving on time and development resources in the first place. Additionally, the commercial CEO wouldn't have to keep writing to members to apologise.
Incidentally, I doubt Code had anything to do with this, I only mentioned them as the zoo have historically outsourced their web builds.
The reporting in that article is questionable, and the text contradictory. "Chester Zoo issues plea to visitors after more than 1,000 'no shows' in a week". Presumably that means over 1,000 people failed to turn up across seven days. Then later: "...on several occasions there have been a number of days where more than 1,000 members who have booked slots, haven't turned up...". So that's individual days? I'd suggest the former is correct.
I find it really shocking that people who supposedly support the zoo act like this. Presumably if the zoo didn't limit the number of free member tickets per day, they might book up all the available slots, robbing the zoo of much-needed income.
It was wholly predictable, and largely down to the increase in members. In 2011 the zoo had 38,500 members, in 2013 they had more than 50,000, and in 2018 they were celebrating 100,000 members. All of them have paid, something in the region of £100 for adults and £60 for children. That's a lot of income already in the bank.
Moreover, you have to look at the visiting habits of annual members, who are used to popping into the zoo for a few hours when the weather is fine, or when there's a new elephant/bear/rhino etc. That's going to be a hard habit to break, and the culture is fostered in part by the zoo who have encouraged such a huge number of members. The fact that here in Chester it keeps raining, really isn't going to help.