bug: phone keeps ringing after picking up the call on a desktop client

[kevrl]

First you need to enable this setting in Rocket.Chat server:
Conference -> Enable mobile ringing (Enabled)

Description
Receiving a videocall in a direct message on your phone and desktop client, will cause the phone to continue ringing after picking up the call

Expected Behavior
The ringing should stop on your phone when you pick up the call on desktop client

Actual Behavior
The phone keeps ringing after picking up the call on desktop client

Versions
Rocket.Chat server version: 7.3.1
Rocket.Chat desktop client: 4.1.2
Rocket.Chat mobile app Android: 4.57.2
Rocket.Chat mobile app Apple: 4.57.2.73496
I'm able to reproduce the issue on both Android and IOS.

Steps to Reproduce

1. Enable the setting on your rocket.chat server: "Conference -> Enable mobile ringing (Experimental)"
2. Open up your Rocket.Chat desktop app
3. Open up your Rocket.Chat mobile app and minimize it to the background
4. Have a friend call you through a direct message (in our case we use Video Call, Jitsi)
5. Check that it's ringing on both phone and desktop client
6. Pick up on desktop client
7. Your phone will continue to ring even though you are already in a call on the desktop client.
8. If you have an IOS phone it will start to ring once you've picked up