diff --git a/src/container/srv_container.c b/src/container/srv_container.c
index bf9ebdeddaa..aca2121457f 100644
--- a/src/container/srv_container.c
+++ b/src/container/srv_container.c
@@ -1712,10 +1712,12 @@ cont_ec_agg_alloc(struct cont_svc *cont_svc, uuid_t cont_uuid,
 	ec_agg->ea_servers_num = rank_nr;
 	ec_agg->ea_current_eph = 0;
 	ec_agg->ea_rdb_eph     = 0;
+	ec_agg->ea_start_ts     = daos_gettime_coarse();
+	ec_agg->ea_warn_slug_ts = ec_agg->ea_start_ts;
 	for (i = 0; i < rank_nr; i++) {
 		ec_agg->ea_server_ephs[i].rank = doms[i].do_comp.co_rank;
 		ec_agg->ea_server_ephs[i].eph = 0;
-		ec_agg->ea_server_ephs[i].ee_update_ts = daos_gettime_coarse();
+		ec_agg->ea_server_ephs[i].ee_update_ts = ec_agg->ea_start_ts;
 	}
 	d_list_add(&ec_agg->ea_list, &cont_svc->cs_ec_agg_list);
 	*ec_aggp = ec_agg;
@@ -1818,9 +1820,25 @@ cont_refresh_vos_agg_eph_one(void *data)
 	int			rc;
 
 	rc = ds_cont_child_lookup(arg->pool_uuid, arg->cont_uuid, &cont_child);
-	if (rc) {
-		DL_CDEBUG(rc != 0 && rc != -DER_SHUTDOWN, DLOG_ERR, DB_MD, rc,
-			  DF_CONT " lookup cont failed", DP_CONT(arg->pool_uuid, arg->cont_uuid));
+	if (rc == -DER_NONEXIST) {
+		/*
+		 * The VOS container can be absent on this target when the container was
+		 * created while the target was excluded, and the following reintegration
+		 * (or extend) did not migrate any record for it. Create it here, otherwise
+		 * this target never reports EC aggregation epoch to the container service
+		 * leader, and the leader keeps the EC aggregation boundary of the whole
+		 * container pinned. The container service leader only refreshes containers
+		 * that still exist in RDB, so it is safe to create the VOS container here.
+		 */
+		rc = ds_cont_child_open_create(arg->pool_uuid, arg->cont_uuid, &cont_child);
+		DL_CDEBUG(rc != 0 && rc != -DER_SHUTDOWN, DLOG_ERR, DLOG_INFO, rc,
+			  DF_CONT " create missing vos container",
+			  DP_CONT(arg->pool_uuid, arg->cont_uuid));
+		if (rc != 0)
+			return rc;
+	} else if (rc != 0) {
+		DL_CDEBUG(rc != -DER_SHUTDOWN, DLOG_ERR, DB_MD, rc, DF_CONT " lookup cont failed",
+			  DP_CONT(arg->pool_uuid, arg->cont_uuid));
 		return rc;
 	}
 
@@ -1850,9 +1868,13 @@ ds_cont_tgt_refresh_agg_eph(uuid_t pool_uuid, uuid_t cont_uuid,
 	uuid_copy(arg.cont_uuid, cont_uuid);
 	arg.min_eph = eph;
 
-	rc = ds_pool_task_collective(pool_uuid, PO_COMP_ST_NEW | PO_COMP_ST_DOWN |
-				     PO_COMP_ST_DOWNOUT, cont_refresh_vos_agg_eph_one,
-				     &arg, DSS_ULT_FL_PERIODIC);
+	/*
+	 * NB: cont_refresh_vos_agg_eph_one() may create the VOS container, which can yield
+	 * and needs a deep stack, so a thread (ULT) collective must be used here.
+	 */
+	rc = ds_pool_thread_collective(
+	    pool_uuid, PO_COMP_ST_NEW | PO_COMP_ST_DOWN | PO_COMP_ST_DOWNOUT,
+	    cont_refresh_vos_agg_eph_one, &arg, DSS_ULT_DEEP_STACK | DSS_ULT_FL_PERIODIC);
 	if (rc) {
 		DL_ERROR(rc, DF_CONT ": refresh ec_agg_eph " DF_X64 " failed.",
 			 DP_CONT(pool_uuid, cont_uuid), eph);
@@ -2094,6 +2116,7 @@ cont_agg_eph_sync(struct ds_pool *pool, struct cont_svc *svc)
 			ec_agg->ea_warn_slug_ts = cur_ts;
 
 		} else if (cur_eph && new_eph > cur_eph && (new_eph - cur_eph) >= 600 &&
+			   (cur_ts - ec_agg->ea_start_ts) >= (new_eph - cur_eph) &&
 			   (cur_ts - ec_agg->ea_warn_slug_ts) >= 600) {
 			ec_agg->ea_warn_slug_ts = cur_ts;
 			D_WARN(DF_CONT ": Sluggish EC boundary reporting. "
diff --git a/src/container/srv_internal.h b/src/container/srv_internal.h
index d53205a4be1..593fbc7d3fd 100644
--- a/src/container/srv_internal.h
+++ b/src/container/srv_internal.h
@@ -69,6 +69,11 @@ struct cont_ec_agg {
 	uuid_t			ea_cont_uuid;
 	daos_epoch_t		ea_current_eph;
 	daos_epoch_t             ea_rdb_eph;
+	/* time when this leader started tracking the container. A boundary jump larger
+	 * than the tracking age cannot have been observed by this leader, it comes from
+	 * the stale epoch loaded from rdb at leader step-up, so it is not a real stall.
+	 */
+	uint64_t                 ea_start_ts;
 	uint64_t                 ea_warn_slug_ts;
 	struct ec_eph		*ea_server_ephs;
 	d_list_t		ea_list;