evar2 is internal search report. Event1 captures search terms and event2 captures null searches. But some of the success searches appear in the null report. Anyone knows how this happens?
When you say Event1 and Event2 did you mean eVar1 and eVar2? Without more information it's hard to troubleshoot what's going on here. I'd suggest making sure you are using events and eVars correctly. Also check on your eVar's persistence.
There is actually a great article on capturing and reporting on internal search terms that I'd also suggest reviewing - https://helpx.adobe.com/analytics/kb/capturing-and-reporting-on-internal-search.html