[Collector]

If a face icon is in the process of loading or being downloaded during a change in network status (ethernet cable coming loose, brief disconnects/high latency, etc.), that face icon will appear as a failed download icon (the page with the x) until the client is restarted. 

Can become a bit iffy and require you to clear the cache sometimes.

[Neus]

This isn't a bug. Just a limitation of the system.