You may see this when editing a fixture of a match where an innings already exists:

This is warning you that you should avoid changing the teams around since there are already players assigned to scorecards. If you have to change the teams then be sure to check you still have the right players on the corresponding scorecards after the change.

Cricket Statz will associate players with teams via their inclusion on the batting scorecard. If you set up a match and enter results (or import results) and then later edit the team fixture and change the team then the associated players will be re-assigned to this new team for this given match. Just be aware of this.