Page URL ‘in use’ message - but it’s not!!

I’m in the process of building my site but have encountered a problem I can’t fathom. As I was building things and deciding where things went I created a page called sports and another page was temporarily called something else, urls were generated automatically and I carried on building. However, I decided I preferred a different lay out and deleted the original sports page and renamed the other to sports instead (deleting and emptying the trash in the process). Unfortunately when attempting to rename the url on the completed page I want to end up with I get an error stating the url is already in use. The url “/sports” doesn’t exist as I had just deleted the page it was on (confirmed by making a link on a page to click on, ends up with a ‘page not found’ message), so I can’t understand why I get an error saying that the url is in use when I try to change a different page to that, when it’s clearly not. 
The site is not yet live but I’d rather not have to start all over again just to get round this weird quirk. Any ideas gratefully received. 

2 hours ago, CaptainBarnacles said:

when attempting to rename the url on the completed page I want to end up with I get an error stating the url is already in use. The url “/sports” doesn’t exist as I had just deleted the page it was on (confirmed by making a link on a page to click on, ends up with a ‘page not found’ message

URL slugs can't match URL slugs for other live pages or pages that are in the trash. You should be able to reuse a URL slug if you have deleted the old page and emptied the page from the trash, although it could be cached for a little while. If you cannot resolve this, please contact Customer Care.

Thanks, yes nothing I do has resolved it. I've looked through every page/gallery etc I've made to see if anything has the same /url name but nope, nothing...it's been like that over a week. It's not isolated as others seem to be behaving the same way.

this works for me every time but it's crazy - don't laugh. 

If my URL is rejected, I separate my original image file, (the one SS won't take) from it's dupes and rename  by adding symbols and numbers (maybe 6 - 7) front and back of the real file name. Then resubmit this altered file

I am an artist and not so concerned that, in the coming years, there will be an issue because of the images with a wrong file name.

Stephen