Scanning for e.g. a rigol-ds device (probably applies to others as well) via TCP if there's no device to answer in the network will make the PV UI hang indefinitely, it has to be killed via "kill -9".
There should be some kind of timeout or other mechanism (in libsigrok and/or PV) to prevent this from happening.
Pretty sure this is what I ran into today when clicking the dropdown to change from a .sr file to a live capture, after resuming my computer from suspend. I got a very very long lockup that made gnome largely unresponsive.