zone-update: fix handling of contents resources when retrying zone_load_diff

src/knot/events/handlers/load.c

@@ -206,6 +206,7 @@ int event_load(conf_t *conf, zone_t *zone)
 					                 "zone file changed with SOA serial %s, "
 					                 "ignoring zone file and loading from journal",
 					                 (ret == KNOT_ESEMCHECK ? "unupdated" : "decreased"));
+					zone_contents_deep_free(zf_conts);
 					ret = zone_update_from_contents(&up, zone, journal_conts, UPDATE_HYBRID);
 				}
 			}

src/knot/updates/zone-update.c

@@ -185,7 +185,16 @@ int zone_update_from_differences(zone_update_t *update, zone_t *zone, zone_conte
 	}
 
 	ret = zone_contents_diff(old_cont, new_cont, &diff, ignore_dnssec);
-	if (ret != KNOT_EOK && ret != KNOT_ENODIFF && ret != KNOT_ESEMCHECK) {
+	switch (ret) {
+	case KNOT_ENODIFF:
+	case KNOT_ESEMCHECK:
+	case KNOT_EOK:
+		break;
+	case KNOT_ERANGE:
+		update->new_cont = NULL; // Prevent deep_free as old_cont will be used later.
+		update->a_ctx->flags &= ~APPLY_UNIFY_FULL; // Prevent Unify of old_cont that will be used later.
+		// FALLTHROUGH
+	default:
 		changeset_clear(&diff);
 		zone_update_clear(update);
 		return ret;