HI there, I suspect Codies is no longer actively supporting OnRush or else this would have been addressed already... but can't hurt to document it, if only for others to avoid purchasing the game on Xbox for now.
As the title suggests... it seems any attempt to join a team, or even play against another in a multiplayer or custom match on Xbox causes one of the party to be kicked from the same session. ie. only one player can be in a session at any time.
Bit of a shame really, as the game was suggested for a Digital Foundry Discord community multiplayer session in the near future &