Here are two pictures of a category page, one, with SmartLink plugin inactive:
https://www.cinemaminima.com/images/illustration/category_pageOK.jpg
With SmartLink plugin activated:
https://www.cinemaminima.com/images/illustration/category_pageBAD.jpg
Also the category RSS feed URI are rendered non-functional when SmartLink is activated. De-activated SmartLinks, category RSS feeds work fine.
Strangely, the catgories may be said to “flicker” when SmartLinks is activated: sometimes a given category page may render, other times, it may not. I have tried various states, i. e., right after a category had been posted to, but that wasn’t consistent either. In any event, de-activating SmartLink made the problem go away 100% of the time.
Also, I have tested the plugin by disabling ALL plugins, and then adding them back one-by-one, to isolate the problem. The instant SmartLink was activated, categories became unstable and mostly disappeared.
I hope this helps — I would really like to use this plugin!