I remember this problem vaguely in older versions of OneNote. What happened was that OneNote only allowed a limited number of characters after a forward slash /

You've got 72 characters after your / so I expect the cut-off is at 70. I don't know of any way around it in older OneNotes. Very small chance it's a Registry setting, if you care to dig in there

Fyi I pasted your example directly and also as plain text in my ON 365 in Win10, and both produced proper URLs—so it's been fixed sometime recently.