pop out dialer behaving strange

when im using the pop out dialer and the phone rings and someone else picks it up, the dailer drop down menu opens up... it never used to do this. 

also, when i am on the phone and a call comes in and someone else picks it up, it does the same thing. 

an additional thing that happens is when im on the phone and an incoming call comes in, it makes my volume drop on the current call im on. it also drops the volume of the current call once the phone call is picked up by a coworker. 

it never used to do this. 

im not sure what i can do to stop this as it is very distracting and im missing parts of sentences from my customers when on the phone with them when the volume drops. we are very busy so this drop down pops up hundreds of times a day after a call answered and audio is dropping out every time a call comes in and and is answered by coworker. 

if the is a setting or solution to this, please advise. 

i also hold out on installing updates as there is always something new to deal with.