Strange bluetooth behavior at Sense

[SunsetRunner]

Hello friends.
First of all, I apologize for English, maybe he will understand. Of course, I read the posts on this topic, found advice on how to run Sense, but this is acceptable if it is a one-time phenomenon. Unfortunately, connecting Sense to your phone via bluetooth is not reliable, or at least behaves strangely. Every time I need to turn off bluetooth on my phone for some other reason and then turn it on again, Sense connects once, sometimes not, about 50% and if it is connected, always incompletely, the FitBit application has to open every time. What happens. I turn on bluetooth, a window appears on the phone asking for a connection, in the section "Paired devices" there is an item "Sense Controls" and in the section "Available devices" there is an item "Sense". I'll confirm the connection and Sense will sometimes connect, other times it won't, so the "crossed out phone" symbol on Sense will sometimes disappear, other times it won't. I noticed that whether the phone connects or does not connect, if I hold the bluetooth icon on the phone, I click on the gear next to "Sense Controls", two more items appear called "Calls" and "Input Devices", both are inactive sliders, whether Sense is connected or not. For the "Input device" item, after clicking on the slider, it becomes active, for the "Calls" item, a message appears stating that the FitBit application is required. Ok, I start the FitBit application, click on Sense -> Alerts and a window asking for a connection will appear immediately. Why so complicated? Why doesn't a phone that is already paired connect directly to the first request after turning on Bluetooth? Please note that I have reset the watch to factory settings, the same for the phone, without any other applications, to prevent bluetooth from interfering with another application, and it still behaves the same. I would like to add that this behavior is also the same whether the phone is connected to the network or GPS is switched on. 
Phone Samsung S22+.

[LokeAa]

@SunsetRunner 

In your Bluetooth connections, when connected, on your phone, you have “Sense” in “Other devices,” and as “Sense controls.” Sense controls is sort of a virtual device, handling on wrist calls, notifications,  headphones.... Sense in “other devices” is your permanent Bluetooth connection between Sense and your phone. In your app settings on the phone, have you given Fitbit all permissions? In the same section, under advanced, battery, have you chosen “do not optimize”? If not, grant all permissions and chose “Do not optimize.”

[Cjvs]

I have recently found that my Fitbit Sense runs out of charge more quickly than a year ago.  Also I discovered today that if I have trouble syncing my Sense or pairing my Sense, then I can solve the problem by charging the Sense fully.  Apparently my phones Bluetooth doesn’t get a signal from my Sense unless the Sense has over 50% charge.  

[Cjvs]

What is Optimizing Advanced Battery for?          I noticed that if I have only 40% charge on my Sense, then my phone doesn’t notice my Sense.  

[LokeAa]

@Cjvs  If you chose "optimize" for the battery in the advanced app settings you prevent the app from staying connected at all times. This is advisable for most apps, but some Apps like Fitbt needs to be connected at all times, to sync, give you notifications etc. These Apps, needs to be set to "Do not optimize" to function correctly.

[Cjvs]

When you say optimize battery in settings, do you mean the iPhone or iPad battery settings or the Sense battery settings? 
      I found an optimize iPhone battery setting where it won’t charge the battery over 80% right away if it knows it will be on the charging cable all night, but that wouldn’t affect Fitbit App from working properly.  

[SunsetRunner]

Hi, this will not be my case, the battery in the watch lasts 6 days, I also tried to move away from the phone in the apartment (panel development) and at 5m it keeps the connection via bluetooth. As soon as I reconnect in the application, the connection is maintained.

[SunsetRunner]

Hi, thanks for the tutorial, I enabled everything except the optimization, I'll try. Thanks again. I will let you know.

[Tracy7873]

My s21plus keeps loosing sense control connection when I hit on sense control says its paired then says can't connect sense control so my Google assistant won't work either I'm fed up unpaired it then pairing it any suggestions to keep it connected please?