Overflow /opt/splunk/var/spool/splunk directory

Hello, We have overflow /opt/splunk/var/spool/splunk directory. It contains **stash.new** files from 2014 year to today. Splunk doesn't clean their itself. We used script **fill_summary_index.py** for clean **stash.new** files but it didn't take desired result. Files in this directory don't clean. I don't can find appropriate method for cleaning these files. Can we to remove manually these files from folder? Please help!