Bedrock doesn’t have real members who make normal loan payments, so there are a lot of delinquent accounts in that training library.
Your custom training environment library uses a snapshot of your real members’ data. Since normal daily processing is done on the CTE, it is inevitable that loan accounts not receiving payments will eventually start appearing as past due. However, because of the quarterly refresh, this will be minimized and hopefully less obvious, especially during the first month or so following the refresh.
Of course, any loans that are already delinquent as of the time the data is refreshed with live files will show as past due on the CTE.