Steps to replicate:

1. Create a page titled 'test of # in the page title' make the body the word 'test'.
2. Create another page
3. Insert the 'include' macro
4. Find the page created in step 1
5. Save page

Result:

The following error is shown:

Unable to render {include} The included page could not be found.

Expected Result:

The include macro loads correctly.