Try a new strap. The elastic will wear over time. Sometimes the sensors in the strap are a problem. I usually replace my strap about every year. I’m in Texas and I sweat. I rinse it after every ride. I notice the sensor pads start to separate from the strap over time.
I have only had one problem with the unit. When replacing the battery i undid the screws, pieces of the threaded part were broken off. They probably were over tightened at the factory. They sent me a new replacement for free.
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