I found an issue on my own forum and the IPS forum. In ACP this leads to an error message, on the forum it leads to no search results.

To reproduce the issue:

Search the IPS forum for this phrase - Searching Your Community

Now select Find results in ... Content titles only

Then run the same search with quotes around the words like this - "Searching Your Community"
 

Strange behavior.

This is still a problem after the 4.3.4 update. 

Yeah, I think there's a problem with ElasticSearch and searching with quotes.