What is up with the sectional symbol for Dyer (2Q9)? Why is there a blue square on top of it?
The blue square is the symbol for the Dyer DME
The discontinuity is because Dyer is extremely close to the intersection of the San Francisco and Las Vegas sectionals, and the AirNav/Avare software probably discarded that inch of pixels when it merged the two charts.
For reference, here's where Dyer is on the Las Vegas sectional.
If you are using airnav.com website, on the far right-hand side of the page titled "Sectional Chart" click the picture. This will take you to a much larger image of the Sectional Chart showing Dyer (2Q9).
Then click on the "blue square" directly over the airport symbol:
and you will see the airport information below on the left side of the page: (this extra information page overlaps the Dyer Airport (2Q9) symbol on the Sectional)