https://fossil.textboard.org/sbbs/tktview?name=812dd05990
When a HTTP request fails, the buffers seem to not be cleaned up.
string-match-p " \\*http textboard\\.org"
In sbbs--*-loader you have a (kill-buffer) right after (read (current-buffer)), but this is missing from the :error branch before the error call. You might also want to clean up even if (buffer-live-p buf) is false. Also note that in sbbs--thread-loader both of your search-forwards are using "#f", even the one with (replace-match "t").
Someone might send this to the sbbs.el person.