Hello, my KW88 is bluetooth disconnected if it's more far than 3 centimeters of

Hello,
my KW88 is bluetooth disconnected if it’s more far than 3 centimeters of my smartphone. I test with another smartphone, it’s the same.

Have-you the same problem ?
And how can i resolve it ?

Same problem on iPhone

I do not have that problem with my KW88, up to 5m separation and still connected.

tested with 2 other iPhone and same problem