mmm.. That might be a combination of the cache or plugin conflict.
Anyway if you encounter the same problem please purge all the caches, then disable all plugins except the Cornerstone. And check the case. If it is working then enable the plugins one by one and check.
It can be that in some rare cases the combination of the plugin may cause the issue. But usually, it is related to the heavy caching of the server and the cache plugins.