BLE connection and screen update issue

whenever BLE connetcion is performed (with or without CALLBACK message) , screen remains in overlap state that you can see in previous attachment.

Yes, that's expected - if you turn off debug messages it'll stop.

What happens is when data is printed to the console (in this case, probably -> Bluetooth) the screen scrolls up - however many watch faces only update part of the screen most of the time, so what was previously on the screen that got scrolled is still there.

Without Debug messages enabled you won't have that problem though.