Grids Row Height Wrong after Button Resize

Hello

I am working on a Cross-Plattform App using Xamarin-Forms - to be exact: a XAML Template for Xamarin Forms. I have a Grid which basically consists of Images, and the idea is to have these Images scaled into the Grid (for that I use ).

This basically works fine, the Images are scaled down a bit - but the problem is the Rows Height is wrong after the scaling.

Any ideas how to fix this problem?

Best regards,
Manuel