This issue is the result of a SQL timeout when loading the application users into the database. When the script times out, the transaction is rolled back. This is why the group members seem to disappear from the DataList. To resolve the issue, users can update the default timeout for that specific type of SQL operation via the web.config file from 3 to 10 minutes using the key:

<add key="SPWrap.DefaultNonQueryTimeout" value="600" />

This seems to allow for enough time for the script to complete. If the problem ever arises again, re-adjusting this timeout or the “REQUEST_TIMEOUT_SECONDS” value could be used to troubleshoot the error.