The action logging in C4/Serials.pm for subscription changes passes an empty string as the info parameter for all logged actions (MODIFY, ADD, RENEW, DELETE). No structured diff is generated in the action_logs.diff column. Affected calls in C4/Serials.pm: - SERIAL/MODIFY (~line 1410): logaction( "SERIAL", "MODIFY", $subscriptionid, "" ) - SERIAL/ADD (~line 1534): logaction( "SERIAL", "ADD", $subscriptionid, "" ) - SERIAL/RENEW (~line 1636): logaction( "SERIAL", "RENEW", $subscriptionid, "" ) - SERIAL/DELETE (~line 1859): logaction( "SERIAL", "DELETE", $subscriptionid, "" ) This bug covers updating these calls to pass meaningful subscription data. Ideally the C4::Serials functions should be refactored to use Koha::Subscription objects so that $subscription->unblessed can be passed as $infos and $original. At a minimum, a subscription hashref retrieved before the change should be passed as $original and the post-change state as $infos.