This is a ‘close relative’ to the ‘eternal boot screen’. It is also caused by the all-mighty triggering system, which governs the whole oscilloscope – even when it shouldn’t. One of the most annoying things is that this can block / halt screen updates and make the thing completely unresponsive to ANY user input – except the power switch.
How to reproduce:
Set the timebase to a large value (say 50s/div) and press the ‘AUTO’ button. The scope will be bricked for 10 minutes!