Watch looses connection to BLE device

I'm author af a data field to interact with treadmills.

A user reported, that his watch (VivoActive 5) looses the connection to the treadmill about every 5 seconds (isConnected() of the device is false).

After pairing, the communication with the treadmills works like that:
The watch is sending a message to the treadmill, which tells the treadmill to send status information back.
The treadmill sends the status information back.
That's repeated, about every second.

There is not much magic, and it works for a lot of other users without any issues.

The user has an RSSI between -55 and -75.

I've also implemented a web-application to test the connection to the treadmill - this works without issues. Also connecting the treadmill to the smartphone app of the manufacturer works without issues.

The user also has no problems with connecting a chest strap to the watch, and the connection to his smartphone is also stable.

I told him to restart his watch (because this once solved Bluetooth issues for me), but it hasn't fixed his problem.

Has anyone an idea, what the user could try, or what I could try to work around this issue?

  • The BLE range on the va5 isn't that good.  (the watch itself).  I have an app that uses BLE to talk to a Raspberry Pi to control my Garage Door.  It often can't connect to the Pi when I'm in my car right outside the closed door.  Other watches I have work much, much better.

    If you look in the forum for the va5 and Venu3, you'll see people mention the BT range when the watch is just trying to use the phone.