Try this:

1. Go to https://piefed.social/search
2. Search for something => search results are displayed, url looks something like this: https://piefed.social/search?search_for=posts&q=test&community=&type=0&language=0&software=&sort_by=&nsfw=&minimum_upvote=&submit=Search
3. From the search results page, perform another search
   => "an unexpected error has occurred"
   => url looks different: https://piefed.social/search?q=test&community=0&language=0&search_for=posts

I also recently noticed that the "fetch a remote post" option doesnt work on piefed.zip at the moment, with "an unexpected error has occured" message. not sure if that is a .zip problem or a Piefed problem, but could be related

Looks like the community parameter is borked. To fix the second url remove the 0 from the community parameter.

Broken
https://piefed.social/search?q=test&community=0&language=0&search_for=posts
Should work
https://piefed.social/search?q=test&community=&language=0&search_for=posts

Yeah...that seems like a pretty clear bug. Should be an easy fix. Thanks!

Ah I've been receiving automatic error reports about the search for a while but couldn't figure out how people were triggering it!