Make sure the phone is mounted correctly. The phone needs to pick up the vibrations from the bike in order to calculate your cadence. For that to work, the phone needs to be placed on the handlebars of the bike in a stable and forward pointing position. If the phone is too wobbly, the signals will get corrupted and you will get a wrong cadence measurement. Use an official phone mount for your bike, or contact us for help finding a 3. party mount that will work. The quality of your cadence data also depends on the sensors in your phone. All iPhones work fine, but some lower end android phones without gyro give more noise results. Search for the phone model on www.phonearena.com and look for Gyroscope (typically next to Accelerometer, under phone features). In general, the app still works without a gyro, but phone mounting becomes even more important. If you have a very bad internet connection, you might also get holes in your data, and the cadence data you do get will be of low quality: contact Motosumo to debug if the internet connection could be an issue.