We're on 08.21.01.0198 (C4110-2 controllers) and have seen this issue since we upgraded in October. The response from the controller is very janky and sporadic. It will be working fine one moment, then hang or respond sluggishly. Clicking refresh will resolve the issue most of the time and the page will pop up as though there was never a problem. Its as though the browser has finished rendering the page in the background but was unable to display it for whatever reason. I've put up with it for now because the refresh generally gets me to where I want to be, but it would be nice to know if this is a known bug and there is a fix for it, even if that means upgrading again.