I am not familiar with it but the security one might have something to do with it perhaps? Let me explain…
A search is extremely database intensive and ‘expensive’. It can also take a while to get the necessary data. So with SP we only run a search query once which is the initial run. We then save off all of the forum/topic keys to a WordPress transient record. When page 2 – or any other page is requested – we simply get the list of keys from that record and then just load the necessary topic data. So basically we cache the results to save running the full search query with every page load.
The transient record database key contains the IP of the user. It also has a timeout on it although this is something like 15 or 20 minutes (I can check on that).
So if (a) there was some kind of block on using transients – or – something that removes them quickly – then that would throw away the search results. Or (b) if the IP address was blocked we would end up with a non-unique key that could quickly get overridden by another user making a search with different row counts.
Understand I am shooting in the dark here. Since V5 was released in February 2012 this is the first report of this kind so it is clearly not a general issue. i think you will find the results of a search on this site are working just fine. So I am trying to figure out what could screw it up.
