Attached is a sample project that can be used to reproduce the issue.
To reproduce the issue, do the following:
1. Start editing any GridView row.
2. Click the Update button
As a temporary workaround, it is possible to clear the EditorPropertiesErrors collection for a corresponding column in the RowValidating event handler:
C#protected void ASPxGridView1_RowValidating(object sender, DevExpress.Web.Data.ASPxDataValidationEventArgs e) {
ASPxGridView gridView = sender as ASPxGridView;
e.EditorPropertiesErrors.Remove(gridView.Columns["OrderTime"]);
}