[Samba] bind crashes after samba upgrade

[Sonic]

Finally biting the bullet and upgrading some old Samba servers.
This particular server is running 4.10.16 and as a first step I'm
attempting to upgrade it to 4.12.15 (I think I remember something
about 4.11.x not handling the upgrade properly).

Samba seems to run OK but bind9 will crash when loading the dns with dlopen:
==================
named[25566]: sizing zone task pool based on 0 zones
named[25566]: Loading 'AD DNS Zone' using driver dlopen
bind9.service: Main process exited, code=killed, status=11/SEGV
kwsrvr01 rndc[25581]: rndc: connect failed: 127.0.0.1#953: connection refused
systemd[1]: bind9.service: Control process exited, code=exited status=1
systemd[1]: bind9.service: Unit entered failed state
systemd[1]: bind9.service: Failed with result 'signal'.
==================
Bind will start fine if I disable referencing Samba's named.conf file
(and I am using the proper version), but of course it's practically
useless without the database.

Any assistance is appreciated.
Thank you,
Chris