I suspect a XAML compiler and/or WPF bug, but I want to make sure I haven\'t done something wrong here (other than trusting the XAML compiler and/or WPF, that is :) ).
Write explicitely into :
value #1
value #2
value #3
I had a very similar issue (actually, quite exactly the same, only with UserControl). I was desperate when I tried the above workaround :), but it worked.
I've just tried it out with your example code now, with explicit it works by me, without it it doesn't.