Also about your last stack ( P-> Z) and uncategorized stack being empty on page load seems like a bug, there is a workaround for this issue ,you can open the sort dialog and click apply again, you will see all cards loads and sort them. We are tracking this issue as a bug internally with tracking ID BUG-004584, we shall let you know when this issue is fixed. Thanks for reporting the issue.
This seems to be a problem with WordPress as it deletes automatically <iframe width="800px" height="400px" src="https://app.spreadsheet.com/workbooks/public/8rwY5lW_RdSk-jPb7oSTeAnScFQG0aTxeaWflKKb4a3g"></iframe> when entered as HTLM-code. The code works with other websites.