[Koha] Koha 20.05 error rebuilding Zebra biblio indices

[Curt & Penny Murley]

Hi Koha Discussion List,

Introduction
============
My name is Curt Murley and I provide tech support for a small public
library in Casco, ME USA.
We are a long time Koha user starting with Koha 2.2 in 2007.

Environment
===========
Our production server is running Koha 20.05.18 installed from a Debian
package on Debian Stretch.
I have set up a new backup server running Debian Buster using the 20.05.x
Debian package and loaded
it using a mysqldump from the production server. With the exception of
catalog searches the backup
server seems to run fine, however the catalog cannot be searched.

Problem
=======
When I try to rebuild the zebra indices using #/sbin/koha-rebuild-zebra -f
-v -b cpl (cpl is the
instance name) I get the following error and of course the Zebra biblios
indices are not rebuilt.
I get the same error for authorities but the authorities indices are
rebuilt.

Error
=====
Zebra configuration information
================================
Zebra biblio directory      = /var/lib/koha/cpl/biblios
Zebra authorities directory = /var/lib/koha/cpl/authorities
Koha directory              = /usr/share/koha/intranet/cgi-bin
Lockfile                    = /var/lock/koha/cpl/rebuild/rebuild..LCK
Use of uninitialized value $biblionumbertagfield in concatenation (.) or
string
at /usr/share/koha/bin/migration_tools/rebuild_zebra.pl line 219.
Use of uninitialized value $biblionumbertagsubfield in concatenation (.) or
string
at /usr/share/koha/bin/migration_tools/rebuild_zebra.pl line 219.
BIBLIONUMBER in :     $
Use of uninitialized value $biblioitemnumbertagfield in concatenation (.)
or string
at /usr/share/koha/bin/migration_tools/rebuild_zebra.pl line 220.
Use of uninitialized value $biblioitemnumbertagsubfield in concatenation
(.) or string
at /usr/share/koha/bin/migration_tools/rebuild_zebra.pl line 220.
BIBLIOITEMNUMBER in : $
================================

Then for every biblionumber exported the following error occurs:
error retrieving biblio N at /usr/share/koha/bin/migration_tools/
rebuild_zebra.pl line 681

Additional Information
======================
1) I have checked that both kohafield='biblio.biblionumber' and
kohafield='biblioitems.biblioitemnumber'
have the correct values in the marc_subfield_structure table for all the
framework codes in the cpl
instance, i.e. 999c and 999d.
2) I have checked the cpl Koha logs in /var/log/koha/cpl and found nothing
that will help me solve this
problem.

Question
========
Does anyone have any ideas how to fix this?