Usually when you don't want them to happen. You just have to take it in stride and carry a roll of paper towels with you at all times. Dogs also take a lot of care. Because of their line of work, these dogs tend to get more injuries than the average pet and because you become very attached to the dog, you tend to pay very close attention to any and all injuries. I would say that the average K9 handler has at least 4 times as much paperwork as an officer without a dog.
Records have to be kept on everything.
These are not only important for your department uses, but mainly for court purposes. If proper records are not kept on the K9 teams activities, a good defense attorney will use this against you. I'm sure you do. Wait til word gets out that you have a trained K9. You will get calls from law enforcement agencies that you have never heard of.