Cache either invalidating or flushing too soon?

I am using your plugin on the site https://www.sunnylandfarms.com. Version 1.5.8

I have the cache timeout set to 9600 seconds and garbage collection at 3200 seconds. I am using the However, after just 5 or 10 minutes, the cache will seem to invalidate. I'll go from 1 second page loads up to 8 second page loads, then once loaded, it's back to normal 1s load times. Walk away for 5 minutes, try to hit the page again, and back to the 8 second load time.

I think this is not normal behavior. If I could just solve this one problem, the plugin will work perfectly for me. Is there any way I can figure out what is happening and try to resolve it?

Start by reproducing the report on sunnylandfarms.com with version 1.5.8, a 9600-second cache timeout, and 3200-second garbage collection setting. Observe the cache state after the reported five-to-ten-minute idle period and determine whether invalidation or flushing occurs early; done means identifying the cause or documenting the missing evidence needed to diagnose it.

Written by the indexing model from the issue text.