I upgraded to the Charge 4 and love it! With one exception - most days I get the preferred sleep stages ribbon indicating your flow between light, deep, REM sleep and awake. Then on some frustrating days it only shows the basic data.
One morning I noticed a note that said you need to sleep with it tight and pushed up high on the wrist to get the sleep stages feedback - but that doesn't always work either.
Any thoughts or tips??
This happened off and on with my prior Alta HR, too.