I have 2 Yealink phones and the app on an Android phone . . .
If the phone rings and I answer on the Yealink the Android phone with the app rings (even while I'm speaking on the Yealink) - and vice versa.
Surely when one of the instrument options ( Yealink (either) or Android) is answered any ringing should stop at once.
I've just answered a call on one of the Yealinks - the Android rang and continued to ring even after I'd hung up the Yealink (it was just a short call with a security code for banking)
It doesn't seem right to me . . . . . - and it best is totally illogical.