Keeping meticulous records on the judging history of every single item and building in ATITD is a task that could very easily consume a lot of processing power and storage space. For this reason, ATITD has been coded to use a special computing algorithm called "hash processing". Hash processing is a widely-used technique that allows game data to be stored in a very efficient manner. This efficiency helps to keep the servers that run ATITD relatively lag-free, and cost-efficient to run.
Unfortunately, the high-efficiency hash technique used by ATITD has one minor drawback: Very occasionally, the algorithm will confuse one player's actions with another. This means that you may encounter a situation where you try to judge an in-game item, or sign an in-game petition, and the system will mistakenly believe that you've already attempted the same action at some point in the past. In technical terms, we refer to such an error as a "hash collision".
The busier an item has been - the more judgements that have been cast on a building, or the more signatures that have been accumulated by a petition - the more likely you are to encounter a hash collision when you try to use that item yourself. For this reason, most judgeable items have an option to "Check Judging History" in their "Utility" menu - if the judging history says you'll be able to affect the item's score, then you can rest assured that you won't encounter a hash collision when you try to use it.
Unfortunately, it's inevitable that most ATITD players will encounter a few hash collisions during their time in the game. The developers apologise for any frustration or confusion that this may cause, but hope that players agree that the advantages - a faster, cheaper game for everybody - outweighs the minor inconvenience of an occasional hash collision.