Perl cache permission warnings occurring occasionally

I was checking out some public warnings because a client noticed the red warning box in the admin interface.

tail -n5 $SEARCH_HOME/log/public-ui.warnings
Fri Oct 12 16:41:59 2018 - Could not open collection cache file /opt/funnelback/lib/perl/Funnelback/../../../cache/raising-children-web-fluster.cfg.cache: Permission denied
Fri Oct 12 16:41:59 2018 - Could not open collection cache file /opt/funnelback/lib/perl/Funnelback/../../../cache/raising-children-web-quicklinks.cfg.cache: Permission denied
Fri Oct 12 16:47:00 2018 - Could not open collection cache file /opt/funnelback/lib/perl/Funnelback/../../../cache/raising-children-web-collection.cfg.cache: Permission denied
Fri Oct 12 16:47:00 2018 - Could not open collection cache file /opt/funnelback/lib/perl/Funnelback/../../../cache/raising-children-web-fluster.cfg.cache: Permission denied
Fri Oct 12 16:47:00 2018 - Could not open collection cache file /opt/funnelback/lib/perl/Funnelback/../../../cache/raising-children-web-quicklinks.cfg.cache: Permission denied

These are the cache files with their permissions:

ll -la $SEARCH_HOME/cache
total 64
drwxr-xr-x.  2 search search  4096 Aug 23 21:11 .
drwxr-xr-x. 18 search search  4096 May  3 09:02 ..
-rw-r--r--.  1 search search 18968 Aug 23 21:11 collection.cfg.default.cache
-rw-r--r--.  1 search search  1324 Aug 23 21:11 funnelback_documentation-collection.cfg.cache
-rw-r--r--.  1 search search   481 Aug 23 21:11 funnelback_documentation-fluster.cfg.cache
-rw-r--r--.  1 search search   497 Aug 23 21:11 funnelback_documentation-quicklinks.cfg.cache
-rw-r--r--.  1 search search   981 Sep 21 11:12 movie-reviews-collection.cfg.cache
-rw-r--r--.  1 search search   582 Sep 21 11:12 movie-reviews-fluster.cfg.cache
-rw-r--r--.  1 search search   508 Sep 21 11:12 movie-reviews-quicklinks.cfg.cache
-rw-r--r--.  1 search search  1532 Oct 16 13:59 raising-children-web-collection.cfg.cache
-rw-r--r--.  1 search search   582 Oct 16 13:59 raising-children-web-fluster.cfg.cache
-rw-r--r--.  1 search search   508 Oct 16 13:59 raising-children-web-quicklinks.cfg.cache

I’m wondering if these files are updated as part of the update process so maybe these errors are because someone made a search query at the time it was updating?

I’ve grown accustomed to ignoring it because we get these warnings all the time, but it’s never a good thing to get into that habit, so I’d like to solve this issue so we actually take notice if there’s important warnings in the future!

So are the permissions set correctly on this folder, or is there something else we should configure to avoid these errors?