It doesn't happen often. I think it's the same old synchronization problem. Try to move one of your players a little bit and press the save button again. I think it helps, but I'm not sure.
A lot of crutches in this game: going to home screen and back to refresh statistics, do this re-saving, hoping that one sub won't happen twice and there are no ghost goals... TE feels sometimes like a sack race -- you can't run, only jump with your legs in a sack, and accidentally fall from time to time =]