Very often your fans can stop. It happens when they overheat or put together. And it is hard to find them. You can take apart most of the fans. You just need to pull the screws out the screwdriver. Sometimes something is preventing the fan from turning. Usually, the matter is in lubricant. It can dry up, fails or something bad can happen too. The number one thing that can help you to clean your fan is an alcohol or q-tip. Clean the shaft by putting in the shaft back you know just jiggle it back and forth we clean the inside. You can use a toothpick.
But it is better to use proper lubricants if you want fans to work more than a month. But actually, you’d better replace your fan if it is wobbling. Then your computer will work as it should.