PHP warning being thrown, Unknown: GC cache entry

We have a server at my work with APC installed on it, and about every 1-2 weeks, all of a sudden this error just starts being thrown and when it is throw it happens a lot. It will be perfectly fine for the whole of the 1-2 weeks, and then it just blows up. The only thing I’ve figured out to do to stop the errors is to restart apache. The website seems to work fine while this is happening, but I am worried that if I don’t restart apache the server it will eventually start to become unstable and start behaving erratically.
When I search for this on Google I found one page that was sort of useful (a PECL bug), and a bunch of pages that were indexed while they were having this error.
I would love to solve this warning or at least figure out more about what the problem is. Thanks for your time!
P.S. The server hosts a few sites and a couple of those sites are using expression engine. Other than that it is pretty much your normal LAMP setup.