10.2 to 10.3 upgrade: Mounting from ufs:/dev/ada0p3.eli failed with error 19.

[zhaghzhagh at openmailbox.org]

Hello

While upgrading my root file-system encrypted FreeBSD 10.2 I ended up 
with a system not being able to boot. The error message is:

...
Mounting from ufs:/dev/ada0p3.eli failed with error 19.
...

Earlier in the boot process:

...
/boot/kernel/kernel text=0xf7a155 data=0xdb810+0x160f88 
syms=[0x4+0xd7fd0+0x4+0x15f114]
/boot/kernel/geom_eli.ko text=0x107cc data=0x4d8+0x134 
syms=[0x4+0x1260+0x4+0x16c1]
/loading required module 'crypto'
/boot/kernel/crypto.ko text=0x20354 data=0x824+0x248 
syms=[0x4+0x1ba0+0x4+0x21fc]
loading required module 'kernel'
---> module 'kernel' exists but with wrong version
Booting...
Copyright (c) 1992-2015 The FreeBSD Project.
Copyright (c) 1979, 1980, 1983, 1986, 1988, 1989, 1991, 1992, 1993, 1994
The Regents of the University of California. All rights reserved.
FreeBSD is a registered trademark of The FreeBSD Foundation.
---> FreeBSD 10.2-RELEASE-p18 #0: Sat May 28 07:06:45 UTC 2016
root at amd64-builder.daemonology.net:/usr/obj/usr/src/sys/GEMERIC i386
FreeBSD clang version 3.4.1 (tags/RELEASE_34/dot1-final 208032) 20140512
XEN: Hypervisor version 3.4 detected.
...

I recall while setting up full disk encryption, I created a tiny 
unencrypted partition for the kernel files, plus there was some tweaking 
with symbolic links between the encrypted and the unencrypted partition. 
(Unfortunately my notes about this are on the unbootable host. I clearly 
remember there was a '/unenc/' directory and some files in it, however 
it was long ago to remember all details...)

What could be the issue? And how could it be fixed?

The 10.2 to 10.3 upgrade went through, only after the 2nd restart it 
stopped booting.

(Strangely I did earlier an upgrade from 10.1 to 10.2 with the same 
setup, and it worked perfectly.)

My 2nd guess is that in the middle of the upgrade the nightly periodic 
job was triggered that might have fetched again 10.2 kernel files. (?)


Thanks in advance for any help!