The graphs are generated from three monitors. It is possible due to hopefully short-term failure of the monitoring servers that no data at all will be collected and graphed. This is not a problem with your line, and you are able to tell the difference between loss, and monitoring system downtime, as the blue 'packet loss' line will also disappear during the outage periods.

We strive to keep the monitoring servers up 24x7 and total gaps should be very rare.