Garbage Character and Flush

I’ve setup W3TC with Amazon Cloudfront and everything appears to be working quite well. The one issue I am having is with the “junk characters” that appear on the full and mobile versions of my site. I assume that term is referring to the “symbol” character of a rectangle that pops up in a few places.

If I totally remove Cloudfront, it goes away. When I add it back in, it comes back. In your FAQ it’s suggested to remove the flush() function but I have no clue where to find that. I checked the .htaccess file for the rewrite rules but did not find it there.

Any other suggestions on how to get rid of this annoyance?

https://www.ads-software.com/plugins/w3-total-cache/