This code returns negative MaxSize on 100% dpi, since it overflows int.
var dpiScaleFactor = radLabel1.RootElement.DpiScaleFactor;
var r1 =
var r2 = TelerikDpiHelper.ScaleSize(r1,
SizeF(1f / dpiScaleFactor.Width, 1f / dpiScaleFactor.Height));
I use that code to descale some sizes on runtime per suggestion on the forum, also I have seen similar code in Telerik sources. When control receives negative max size it becomes invisible. You may want to investigate this cases.
I use Telerik 2018.3.1016.20 with .Net 3.5 on Server 2008 R2 SP1.