Ya, once I completely disabled the cache in our IIS ARR server which is acting as a reverse proxy the problem went away. I also have a SharePoint environment running claims authentication which passes through the same proxy and the cookies are not cached so I do wonder if Sitefininty doesn't properly mark the authentication cookies to not be cached.
Specifically what I did is went into the caching settings on the ARR farm and set the memory cache duration to 0 and unchecked enable disk cache and set query string support to do not cache. Also from the root IIS server node i went into output caching -> edit feature settings and unchecked all the boxes.
I had no actual need for caching for any of the sites passing through my ARR server so completely disabling caching was acceptable for me. I don't remember if i tried just disabling it in the farm first but i feel like I may have.