Replace the team if the team is changed during the round. Also replace the whole team if only one player is replaced (except if they have not yet played any matches).
The reason is that all historical match results are on the team. If you replace players, the new players inherit the team's match history and the old players lose their history.
Follow the following instructions to replace a team:
1. Add the new team to the list of teams, see here
2. Go to Current round/Groups
3. Click on Players in the group they play
4. Delete the team to be removed (or moved to another division)
5. Add the team to be entered