Xamarin.Firebase.Crashlytics Causes AAPT2 Build Error

When I have Xamarin.Firebase.Crashlytics installed in my Xamarin.Forms app, the build fails with the following error:

Unknown option -RF:\...\flat\drawable_avatar6.png.flat. Please check$(AndroidAapt2CompileExtraArgs) and $(AndroidAapt2LinkExtraArgs)to see if they include any aapt command line arguments that are nolonger valid for aapt2 and ensure that all other arguments are validfor aapt2.

I've spent three hours trying to diagnose the issue and I'm utterly flummoxed. Uninstalling Crashlytics removes the problem so it definitely is the cause. However, it seems only to happen since I updated VS2019 to v16.10.4 but I can't be sure that that's part of the problem.

Both Xamarin.Firebase.Crashlytics v118.01 and v117.4.1 cause the problem. The Android SDK build tools are up-to-date.

avatar6.png appears to be something to do with Syncfusion.Xamarin.Core although I suspect that's a red herring.