I don’t see the gaps in the mlat positions we generated, but your receiver (not sure which of your receivers you were looking at specifically, but they all show the same sort of thing) did not participate continuously.
The cause is probably that you are in a very densely covered area and so the mlat server picks only a random subset of receivers for each aircraft. The receivers are re-selected periodically. There is a grace period where you will continue to receive results even after being deselected but with enough receivers in an area you can go without being selected for long enough that the results stop until you’re reselected.