Now refresh that in your browser a few times with CTRL+F5. You will see, that the prerequisites change without reason! Very visible on the first entry, where 350 appears and disappears.
I spend 30mins trying to figure out why my program doesn't aggregate the data correctly for different languages...
Where it might be seen much better: Download the URL https://api.guildwars2.com/v2/guild/upgrades?ids=all several times and compare the filesizes
Downloaded the ids=all URL 100 times with wget. I got 27 different filesizes (in byte)
Was I able to help you or give you a hint? Click on Helpful and/or Thumbs up, I would appreciate it alot!
When you encounter a bug ingame, at first you should file a ticket via the ingame command /bug, as only this way the devs will know exactly where you were, when the bug happened.