Street names on map erratically displayed.

When using Map or Walk, I note that both my D2 Delta and 5+s only erratically (and quite randomly) display street names. This is using both the default Garmin Topoactive map and the Garmin full Topo map (Australia/New Zealand).

I was thinking the CPU is otherwise tied up with GPS telemetry and the like but during an active session, simply changing the zoom level repopulates all the displayed street names until they scroll off the screen leaving random street name entries on the redrawn segments.

Do others have this nuance?