Editing Parent Categories is changing the slug to -1

Hi,

I have recently been editing my categories (only content & seo) and have noticed that any category which is a parent category is having it’s slug changed so it is appended with -1. This is happening in both places and events CPT.

I know about the better search result plugin and finding the slug in myphpadmin but it seems to me there must be something else going on here, why would they change as a result of simple edits, why is it only affecting parent categories?

Any advice would be appreciated.

Thanks,

Tristan.