Earlier I was trying to respond to a thread and attempted to include multi-tag searches via the URL.
The website generates me this URL:
https://www.fakku.net/search/+petite%20+busty
Which worked but then sometimes clicking the URL tells me no search results could be found.
So after experimenting a bit with tags, I've come to realise that it's not just multi-tag searches like I originally thought, but the tag search function as a whole. Even major tags like vanilla can crap out and bring up this same error from time to time.