To reproduce:
1. display the Map page. In this example I have custom maps disabled (via MapManager)
2. select Menu > Map Layers
3. both TopoActive and CityNavigator are displayed and enabled
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6. TopoActive is still being displayed (although the Map Layers showed it as being disabled)
When pressing Enter instead of Down in step 4, both TopoActive and CityNavigator become disabled (I would expect only TopoActive becoming disabled). Quitting to the Map page then correctly only shows the basemap. Changing the selection with Up and Down after pressing Enter to disable the TopoActive layer will not change the selection state of both Map Layers.
When pressing Up / Down and Enter a couple of times in the Map Layers, sometimes the custom maps on the device will get enabled. Have not found the exact steps to reproduce this.
So it looks like there is a bug in the Map Layer selection handling?