did the upgrade on my Xperia X yesterday (my daily use device. The "for tests" Jolla 1 was done earlier)

Like for a few other users, when reaching 100%, the upgrade process stops and freezes instead of rebooting into the fresh new system as it should.

Did take a few step to investigate.

the Xperia X is showing on the USB bus.

but it doesn't show on the network (I've set it up to to automatically default to "dev mode")

in fact it's not showing up as a usb-network device at all.

it shows up as a Linux File-CD Gadget (a type of hybrid device that both shsows up as flash (e.g.: /dev/sde) and as an emulated CD-ROM drive (e.g.: /dev/sg1) )

LOLWUT?!?

forcing the reboot manually (power + volume up) brings everything back to normal and boots into the brand new 2.2.1.18

Seems to me that it's linked to something on the Qualcom SoC ('s firmware ?) going bonkers instead of performing the necessary reboot.