No more voice chat against more then 8 people

Hello, we try to play Forza 7 as multiplayer and even when we are more then 8 people we get disconnections to the 9th and next players.

We use this game as cross platform, some players have PC, some other Xbox

The hosters Nat is open

We have tried to enable 2 parties, one for the chat, and the next one for the game (the multiplayer inside Forza 7). It has Problems, the PC Players seems to be enabled two times inside the voice chat. They have double voices. In this scenario always the 9th
player, and further, are disabled from voice caht.

Also, if we tried only one multiplayer session, only the one from inside Forza 7, the 9th player have some disadvantages.

Even so, the 9th player and further is disabled from voice chat.

If we only enable a voice chat Session with 11 or 12 players, it works fine. We all can talk together.

If we then enable the Multiplayer inside Forza 7, all players are on the Table.

If we now try to start a game or to change some play parameters, e. g. tracks, some people went out the multiplayer.

Then we try again and again to start the multiplayer, even so long as we all in the multiplayer table.

If so some people doesn’t have voice-chat, game itself functions are available.

It is always the same, more then 8 player can not have voice chat even when the multiplayer game is active.

If we play with 4 or 5 players all works fine. Any suggestion?

:)