Comment # 1 on bug 1139967 from Stefan Hundhammer

Well, the application is busy at that time, so it can respond only when it gets
a time slice to work in. That is usually when libzypp (while executing some
external "rpm" command) calls the "update the progress bar" callback, i.e. when
the rpm command sends a new percent number.

When some lengthy post-install script or something similar is called, there is
no such callback in between, and it may take a while until the YaST application
can react to a user event.

X11 forwarding via ssh has its own challenges these days: Qt used Xlib
primitives before Qt 5.x, but since Qt 5.x it renders everything into a pixel
buffer and then just copies that pixel buffer to the display. While this is
blazingly fast with a local X11 connection, this is really slow over remote X11
(and there is nothing that we can do about that; it always uses that kind of
rendering from Qt 5.x on).