Same here. Simply uploaded the npk file, and reboot.
Then, boot loop!!.
Tried everything I found online, none of that works.
Netinstall can’t even find the device.
Hopeless.
Netinstall 7.12 could find my bootlooped RB850Gx2 , Netinstall 6.49.10 could not…
When upgrading to 7.12 via Netinstall, I saw that the progress bar went ‘beyond’ 100%, back to 0% and stopped at around 5% before the ‘reboot’ button got visible. As if the ppc version is ‘to big’ for the RB850Gx2 .
I ran into this as well. Fortunately was able to recover the router via netinstall. I reattempted the upgrade and the same thing happened. I didn’t need to the wipe the config so I’ve submitted a support ticket with supout.rif, hopefully MikroTik can figure this out.
Update from support - this has been fixed by the dev team and a new release will be out soon. Check the release notes to make sure this is mentioned before upgrading, in case another release comes out first.