diff --git a/openair2/LAYER2/NR_MAC_gNB/gNB_scheduler_primitives.c b/openair2/LAYER2/NR_MAC_gNB/gNB_scheduler_primitives.c
index 9b6528d7b0..7c4322f654 100644
--- a/openair2/LAYER2/NR_MAC_gNB/gNB_scheduler_primitives.c
+++ b/openair2/LAYER2/NR_MAC_gNB/gNB_scheduler_primitives.c
@@ -2809,6 +2809,30 @@ int nr_mac_enable_ue_rrc_processing_timer(gNB_MAC_INST *mac, NR_UE_info_t *UE, b
   return 0;
 }
 
+void nr_mac_release_ue(gNB_MAC_INST *mac, int rnti)
+{
+  NR_SCHED_ENSURE_LOCKED(&mac->sched_lock);
+
+  nr_rlc_remove_ue(rnti);
+  mac_remove_nr_ue(mac, rnti);
+
+  // the CU might not know such UE, e.g., because we never sent a message to
+  // it, so there might not be a corresponding entry for such UE in the look up
+  // table. This can happen, e.g., on Msg.3 with C-RNTI, where we create a UE
+  // MAC context, decode the PDU, find the C-RNTI MAC CE, and then throw the
+  // newly created context away. See also in _nr_rx_sdu() and commit 93f59a3c6e56f
+  if (du_exists_f1_ue_data(rnti)) {
+    f1_ue_data_t ue_data = du_get_f1_ue_data(rnti);
+    f1ap_ue_context_release_complete_t complete = {
+      .gNB_CU_ue_id = ue_data.secondary_ue,
+      .gNB_DU_ue_id = rnti,
+    };
+    mac->mac_rrc.ue_context_release_complete(&complete);
+
+    du_remove_f1_ue_data(rnti);
+  }
+}
+
 void nr_mac_update_timers(module_id_t module_id,
                           frame_t frame,
                           sub_frame_t slot)
@@ -2823,8 +2847,7 @@ void nr_mac_update_timers(module_id_t module_id,
     NR_UE_sched_ctrl_t *sched_ctrl = &UE->UE_sched_ctrl;
 
     if (nr_mac_check_release(sched_ctrl, UE->rnti)) {
-      nr_rlc_remove_ue(UE->rnti);
-      mac_remove_nr_ue(mac, UE->rnti);
+      nr_mac_release_ue(mac, UE->rnti);
       // go back to examine the next UE, which is at the position the
       // current UE was
       UE--;
@@ -2963,7 +2986,7 @@ void prepare_initial_ul_rrc_message(gNB_MAC_INST *mac, NR_UE_info_t *UE)
 void nr_mac_trigger_release_timer(NR_UE_sched_ctrl_t *sched_ctrl, NR_SubcarrierSpacing_t subcarrier_spacing)
 {
   // trigger 60ms
-  sched_ctrl->release_timer = 60 << subcarrier_spacing;
+  sched_ctrl->release_timer = 100 << subcarrier_spacing;
 }
 
 bool nr_mac_check_release(NR_UE_sched_ctrl_t *sched_ctrl, int rnti)
diff --git a/openair2/LAYER2/NR_MAC_gNB/mac_proto.h b/openair2/LAYER2/NR_MAC_gNB/mac_proto.h
index 9f96a0d106..e58d2c12ae 100644
--- a/openair2/LAYER2/NR_MAC_gNB/mac_proto.h
+++ b/openair2/LAYER2/NR_MAC_gNB/mac_proto.h
@@ -443,6 +443,7 @@ void abort_nr_dl_harq(NR_UE_info_t* UE, int8_t harq_pid);
 
 void nr_mac_trigger_release_timer(NR_UE_sched_ctrl_t *sched_ctrl, NR_SubcarrierSpacing_t subcarrier_spacing);
 bool nr_mac_check_release(NR_UE_sched_ctrl_t *sched_ctrl, int rnti);
+void nr_mac_release_ue(gNB_MAC_INST *mac, int rnti);
 
 void nr_mac_trigger_ul_failure(NR_UE_sched_ctrl_t *sched_ctrl, NR_SubcarrierSpacing_t subcarrier_spacing);
 void nr_mac_reset_ul_failure(NR_UE_sched_ctrl_t *sched_ctrl);
diff --git a/openair2/LAYER2/NR_MAC_gNB/mac_rrc_dl_handler.c b/openair2/LAYER2/NR_MAC_gNB/mac_rrc_dl_handler.c
index ea0d08e152..75357ef4ae 100644
--- a/openair2/LAYER2/NR_MAC_gNB/mac_rrc_dl_handler.c
+++ b/openair2/LAYER2/NR_MAC_gNB/mac_rrc_dl_handler.c
@@ -466,27 +466,24 @@ void ue_context_release_command(const f1ap_ue_context_release_cmd_t *cmd)
 {
   /* mark UE as to be deleted after PUSCH failure */
   gNB_MAC_INST *mac = RC.nrmac[0];
-  pthread_mutex_lock(&mac->sched_lock);
+  NR_SCHED_LOCK(&mac->sched_lock);
   NR_UE_info_t *UE = find_nr_UE(&mac->UE_info, cmd->gNB_DU_ue_id);
+  if (UE == NULL) {
+    LOG_E(MAC, "ERROR: unknown UE with RNTI %04x, ignoring UE Context Release Command\n", cmd->gNB_DU_ue_id);
+    NR_SCHED_UNLOCK(&mac->sched_lock);
+    return;
+  }
+
   if (UE->UE_sched_ctrl.ul_failure || cmd->rrc_container_length == 0) {
     /* The UE is already not connected anymore or we have nothing to forward*/
-    nr_rlc_remove_ue(cmd->gNB_DU_ue_id);
-    mac_remove_nr_ue(mac, cmd->gNB_DU_ue_id);
+    nr_mac_release_ue(mac, cmd->gNB_DU_ue_id);
   } else {
     /* UE is in sync: forward release message and mark to be deleted
      * after UL failure */
     nr_rlc_srb_recv_sdu(cmd->gNB_DU_ue_id, cmd->srb_id, cmd->rrc_container, cmd->rrc_container_length);
     nr_mac_trigger_release_timer(&UE->UE_sched_ctrl, UE->current_UL_BWP.scs);
   }
-  pthread_mutex_unlock(&mac->sched_lock);
-
-  f1ap_ue_context_release_complete_t complete = {
-    .gNB_CU_ue_id = cmd->gNB_CU_ue_id,
-    .gNB_DU_ue_id = cmd->gNB_DU_ue_id,
-  };
-  mac->mac_rrc.ue_context_release_complete(&complete);
-
-  du_remove_f1_ue_data(cmd->gNB_DU_ue_id);
+  NR_SCHED_UNLOCK(&mac->sched_lock);
 }
 
 void dl_rrc_message_transfer(const f1ap_dl_rrc_message_t *dl_rrc)