Hello dammy35,
The key to finding a solution to an issue like this is to isolate what is causing it.
In this case we would suggest following these steps:
- Start a FaceTime call with just two people
- Add another person to the call
- Test
- Add another person
- Test again
Continue this process until the call drops. Repeat it again and confirm if it happens when the same contact is added each time.
This will help isolate exactly where the issue is originating. Once that is determined, you can work on finding a solution.
You can also try the suggestions in this article to help with troubleshooting:
If you can't make or receive a FaceTime call on your iPhone or iPad
Have a good day.