Same problem here, with a few interesting extras.
I like to audition different cabs and cab IRs with my favorite amps.
The Mark II C+ is a good example of using snapshots to switch between channels.
Using snapshots should fix the preset switching gap problem however, going from normal to lead with a snapshot creates a pretty loud pop.
But I digress....
Anyway, I like using a different cab between the clean and lead snapshots.
That's when audio output disappears or a few times I got a squealing sound and the Stadium locks up.
Reboot time...
Sometimes it doesn't seem to complete.... it hangs.
After few tries it finally boots completely, but the scribble strips are blank.
So I mess with the global setting footswitches and voila, scribble strips appear.
Did I digress again?
I've done many troubleshooting steps, including the nuke and pave method.
As soon as I start adding IRs and Showcase stems, the bugs emerge.
Must be some serious code memory leaks going on, who knows.
Aside from this, the sounds I'm dialing in are great.
I have submitted a ticket and they have quickly responded but no solution as of yet of course.
Can you imagine what customer support is going through?
Meanwhile I'm not mad, I knew the job was dangerous when I took it.
EC