If the screen turns grey that means the container shut down or became unresponsive for some reason.
Under normal circumstances, the heartbeat mechanism is used to shut down containers that are no longer in use, e.g. when the user closes the browser tab. But if the container is shut down while the tab is still open, that may indicate a problem with the heartbeat mechanism. On the other hand, if that were the case, then the screen should grey out after 1 minute, not 10...
You can try increasing the heartbeat timeout value (in millisec) using this property: heartbeat-timeout: 60000