Unable to delete SharePoint site

I have a SharePoint site which was part of a Microsoft Team. The Team has been deleted, however I cannot delete the SharePoint as in the site assets section there is a notebook file which is of the notebook type - "staff_edu". I cannot delete the site due to this file. There are no labels and retention policy set which is stopping the deleting of the file or the site. I am able to delete everything else in the site, the site is no completely empty other than the contents of sites assets.
How can I delete this file and the SharePoint site.

I have tried deleting the site via Powershell
Remove-SPOSite -Identity https://xxxxx.sharepoint.com/teams/YYYY  -NoWait

I get this error message -
Remove-SPOSite : The label that's applied to this item prevents it from being edited or deleted. Check the item's label for more details.

When I try to delete notebook file, I get the error message -"result cancelled by event received" 

I have tried to see if there are any hidden labels in place but there are none - using 
https://sharepoint.stackexchange.com/questions/306441/remove-sposite-the-label-thats-applied-to-this-item-prevents-it-from-being-ed

What else can I check/do to delete this site?

Thanks in advance