The R&S is actually a poster boy of bad practice lately in "Big Brand" crowd. They released RTB2000/RTM3000/RTA4000 equally non finished. It seems they try to lead by bad example here.
My MXO4 serial decoding locked up on first use. They have fixed it though, it was a rather obscure bug where I was adjusting the baud rate too fast and having something else on.
Around 6:40 is the problem
FWIW, I've been playing around with an R&S MXO4 for the past two days and have had the acquisition system stop acquiring samples under certain circumstances - much like what you were seeing in your video. All channels seem dead/frozen. This has happened 6 times so far and the only solution is a power-cycle. It seems to happen when you change the samples/sec setting rapidly (either directly through the acquisition menu using the knob, or indirectly via other actions like changing the sweep rate back and forth). I also had the UI crash once. I'm not sure what caused that, but it happened about a second after I turned on the spectrum window. In this case, the entire screen was frozen (including the clock in the corner) and all buttons - including power - were non-functional.
...And I've noticed at least another half-dozen minor UI bugs, like for example - where the measurement statistics table is not properly exposed when you turn it on and the only way to get it show is to toggle it off/on in the measurement menu.
Clearly the firmware isn't quite ready for prime-time.
On the other hand, even with the bugs, it's an amazing scope. The spectrum display, in particular, is probably the best I've seen on any scope regardless of price. Incredibly fast and behaves like a high end spectrum analyzer. It's such a huge contrast to the toy "math" FFTs found on most other scopes.
A bit off-topic for this thread - sorry.