When trying to put a hold on a record from staff interface: https://staff-master.sandboxes.biblibre.eu/cgi-bin/koha/reserve/request.pl?borrowernumber=1&biblionumber=4712 Template process failed: undef error - The given date (2004) does not match the date format (iso) at /kohadevbox/koha/Koha/DateUtils.pm line 204. at /kohadevbox/koha/C4/Templates.pm line 127
That was due to data on a record not being in the proper format. After removing the publication date (210d and 211a) the issue didn't appear anymore. Not a bug.