Hi all, Running Koha 20.05.06 on Ubuntu 18.04 with Elasticsearch 6.8.13: I have 318 bib records; ~420,000 authority records When running the following reindexing command (authorities only): koha-elasticsearch --rebuild -d -v -a library2 I get the following error just before it commits 10,000 records: [27771] Indexing authorities [27771] 1000 records processed [27771] 2000 records processed [27771] 3000 records processed [27771] 4000 records processed [27771] 5000 records processed [27771] Committing 5000 records... [27771] Commit complete [27771] 6000 records processed [27771] 7000 records processed [27771] 8000 records processed [27771] 9000 records processed [27771] 10000 records processed [27771] Committing 5000 records... Use of uninitialized value $tag in hash element at /usr/share/perl5/MARC/Record.pm line 202. Use of uninitialized value $tag in regexp compilation at /usr/share/perl5/MARC/Record.pm line 206. Use of uninitialized value $tag in hash element at /usr/share/perl5/MARC/Record.pm line 207. Can't call method "tag" on an undefined value at /usr/share/koha/lib/C4/Heading.pm line 71. Something went wrong rebuilding indexes for library2 At this point, I can confirm that 5000 authority records have been indexed, but that's about 415,000 short :S A couple other things: - My node is running when I curl localhost:9200. Top also shows ES running. - I have the ICU analysis plugin installed as well. Never seen this error before. I was running ES 5.x but upgraded to 6.x recently. Could the error above be related to 6.x? If so, can the errors be resolved? Any help would be much appreciated! C Craig Butosi, MA, MLIS, B Mus (Hons) Library: library.craigbutosi.ca