There's a simple way to resolve all of this. Have an automated system set up for the rewarding of items. Most of the events hosted have very simple winning conditions. Something like a player reaching a specific spot in the level first is extremely easy to detect and shouldn't require an admin to judge (assuming fair play, but more on that later).

An event would be hosted by an admin who would nominate a prize set to use for whoever wins the event. The prize set would typically consist of a hat and its recolours. If a player already has all the items in the prize set, they would be awarded a nominal amount of graalats instead. The prize sets themselves would be established by a more senior member of staff( presumably someone who knows what they're doing).

An admin hosting an event should only have the responsibility of overseeing ( but at no point engaging with players) to ensure fair competition (i.e. no speed boosting, etc...), punishing players when necessary.