Automatic redial after call transfer

[PCGYeah]

We have an issue at a site where we installed 10 yeahlink t46g phones, that are connected with a broadsoft voip platform.

An external caller (A) dials the sites phone number. It is picked up by phone B at the site. They then transfer (blind) the call to her colleague (phone C), B hangs up and the call is transfered.

A and C are succesfully connected and we have audio etc...

When C now ends the phone call, a call is automatically beiing iniated from B to C. While B doesn't touches her phone. This happens with every call that is internally transfered, blind...

When they dont transfer the call blind, but when B and C first talk to each other, (attented) to announce the call, this behaviour doesn't happen.

The provider doesn't have a clue , it looks like an "automatically redial when busy" is happening or something...is this an option in the phone?