Dalton Mangrum@Epoch Solutions Group here.
I spoke with a few of you about this issue last week at the Dev Summit and you suggested that I update the Xamarin Forms NuGet packages to see if it fixed the issue.
I went ahead and updated all of the NuGet packages in our solution and did a fresh deployment to our iPad and I'm still seeing the issue.
In an effort to determine if the issue is related to the Esri.ArcGISRuntime.Xamarin.Forms v100.0.0 assembly or our code, I went ahead and created a simple, out of the box ArcGIS Runtime Xamarin Forms app and deployed it to our iPad and I'm still seeing the issue.
I'm seeing the issue on an iPad Air 2 (MH312LL/A) running iOS v10.2.1.
I have not been able to reproduce it on an iPad Air 2 simulator/emulator or an Android device or simulator/emulator.
I've also confirmed that this issue happens regardless of basemap type (online, local tpk, local vtpk).
The issue is quite easy to reproduce. Simply create a simple ArcGIS Runtime Xamarin Forms app and deploy it to your iPad device.
Once the application has launched and the vector basemap is visible click the home button on the iPad to suspend the application, then either click on the application shortcut on the home screen, or double click the home button to list the running apps and select the application.
If you do this enough times eventually you will see the basemap rendering issue on resume I am referring to. (Screen shots attached to this post to visually demonstrate what I'm referring to.)
If you look at the debug output in the attached screenshots you'll see that both the MapPage & MapView always have the same dimensions OnStart & OnResume regardless if the basemap renders properly.
Can someone look into this issue or provide a temporary work around if it's already known?
Let me know if you have any questions or need anymore information.