https://github.com/SparkDevNetwork/Rock/issues/5328
There seem to be some issues with group scheduling. In v14 and 14.1. You might check to see if you can recreate the issue on either the 9 Embers demo site or the Rock demo site. If you can, then it's a Rock bug that probably need to be reported. If not, then you will probably need a dev to look into it.