I have reproduced this on mako with the 16.3 build
Call the ubuntu phone, ring a couple times, hang up
repeat this until the ubuntu phone does not ring, and may or may not not show the notification
call again, let ring, then hangup
wait 10-60 seconds and ubuntu phone will call
note I never touch the ubuntu phone and control the calls from my other mobile
this will happen if the dialer app is running or not
I have reproduced this on mako with the 16.3 build
Call the ubuntu phone, ring a couple times, hang up
repeat this until the ubuntu phone does not ring, and may or may not not show the notification
call again, let ring, then hangup
wait 10-60 seconds and ubuntu phone will call
note I never touch the ubuntu phone and control the calls from my other mobile
this will happen if the dialer app is running or not