Yep, the sequence is exactly as you described. In answer to your questions:
The player shut itself down as I was listening to it, as it did previously when I was out with it. The difference is, the first time with 3.0 firmware it was in my pocket. So, I assumed, as you've alluded to, the unit did it's job & just shut down as it may have been too hot.
Last night on version 3.1 it was just sat on a table beside me & the ambient room temp was pretty cool, about 18c. The player didn't reboot on either occasion, simply shut down. I rebooted it immediately without delay, the difference being on the second occasion the revised system settings were lost.
I sincerely hope as you say it's a glitch & not an inherent problem with my unit but, felt it prudent to mention it, just in case. I've waited some months for the updates for the unit to be useable to me, particular with the functions I so desire, like the play through, which I greatly appreciate. The unit itself sounds incredible. I've had advice from someone else on head-fi with regard Westone W60s I bought to use with this. I was distinctly underwhelmed with them but, they're starting to pay off.
I'm listening to it now & if the fault replicates I'll report back again. No popping when album art changes & the folder play through seems to work. Thank you to all at Cayin