Please note that the plastic of the Move ECG is strong, but can still be scratched or broken. While the warranty of the watch does not cover physical damage such as scratches or broken plastic, we encourage you to reach out to Customer Service here with a picture of the damage.
https://support.withings.com/hc/en-us/sections/4411845138449-Move-ECG
https://support.withings.com/hc/en-us/sections/360003273634-Maintenance