Problems changing the name of the download template page

I’ve been trying to change the name of the download page to pre-order.

Under page settings > Page Title & URL, I changed the name to Pre-order, and also the box directly below it to pre-order.

However, when I click update the name under Title & URL changed back to Download automatically.

Now I have broken links.

Please let me know what I should do?

Thanks,

Jenny