This is reproduced by setting windows to aero and setting the xamRibbonWindow Resize to NoResize.
I was able to reproduce the issue and it should be addressed in the next hotfix. You should contact the support group and reference issue 15153 so you can be notified when the hotfix is available.
I still see the similar issue of "Application title" being missing, when XamRibbonWindow's WindowState="Maximized" and connected to multi monitor screens in Extended mode.
Note: When Project mode (Windows + P) is Screen only, title shows up properly. And this issue happens with empty XamRibbonWindow sample project too.
Infragistics version using: 19.1.20191.208
Please suggest!