The sketch editor does not seem to record the correct coordinate, when the magnifier is used on an iOS device.
In order to replicate the issue, i have attached a video <ArcGIS Runtime Sample, "Sketch graphics on the map">.
Notice, in the video i am trying to draw a polyline.
..Long pressing on the map to invoke the magnifier, when i lift my finger to stop the magnifier the graphic point does not fall in the same location as the magnifier, instead i see the graphic point in the North-West.
The same sample works fine on an Android Device.
I am using
ArcGIS Runtime 100.4.0
Xamarin Forms 3.5
Device with iOS 12.1.4