Active minutes went crazy

[Derfel84]

I started using again my Fitbit Charge 5 after some months.

The tracker started counting active zone minutes without any sense (when I am sit at work, for example). It counted 240 active minutes in 4 hours...

I saw in the forum that some people had similar issues because they had the standard 1900 date of birth in their account, but is not my case. 

I would avoid to buy another tracker, it has less than 2 years. Any suggestion?

[JohnnyRow]

Your tracker does not measure "active zone minutes" per se.  AZM are derived from other data that you can check.  First, it depends on your heart rate, so check if your heart rate looks reasonable, especially during the time you were getting AZM.
Second, your heart rate had to be at least as high as your moderate heart rate zone.  Your heart rate zones can be seen by clicking on the Zone Minutes circle near the top.  These depend on your age and resting heart rate.  So check your birth date is correct, and RHR looks reasonable.  It's probably a good idea to remember about what this heart rate is to start getting zone minutes in the future.