diff --git a/KNOWN_ISSSUES.md b/KNOWN_ISSSUES.md
new file mode 100644
index 0000000..e54fe04
--- /dev/null
+++ b/KNOWN_ISSSUES.md
@@ -0,0 +1,34 @@
+
+## `matching-onu-port-label-invalid` error
+This happens after olt is rebooted.
+
+```
+20190419T230010.719 ERROR    MainThread openolt_data_model.__onu_ports_down {'onu_port_id': 'PON port', 'onu_ports': [port_no: 100
+label: "PON port"
+type: PON_ONU
+admin_state: DISABLED
+device_id: "0001f2c9e5b98ce4"
+peers {
+  device_id: "00010d5c85383648"
+  port_no: 16
+}
+, port_no: 16
+label: "uni-16"
+type: ETHERNET_UNI
+admin_state: DISABLED
+device_id: "0001f2c9e5b98ce4"
+], 'vcore_id': '0001', 'error': KeyError('key id=PON port not found',), 'instance_id': 'vcore-0_1555714355', 'olt_id': '00010d5c85383648', 'onu_id': '0001f2c9e5b98ce4', 'event': 'matching-onu-port-label-invalid'}
+20190419T230010.720 DEBUG    MainThread openolt_data_model.__onu_ports_down {'instance_id': 'vcore-0_1555714355', 'vcore_id': '0001', 'event': 'onu-ports-down', 'onu_port': port_no: 16
+label: "uni-16"
+type: ETHERNET_UNI
+admin_state: DISABLED
+device_id: "0001f2c9e5b98ce4"
+}
+```
+
+## `rx-in-invalid-state` error message in mib_sync.on_set_response
+This happens after olt is rebooted.
+
+```
+64988 20190419T230147.166 ERROR    MainThread mib_sync.on_set_response {'instance_id': 'vcore-0_1555714355', 'vcore_id': '0001', '      state': 'uploading', 'event': 'rx-in-invalid-state', 'device_id': '0001f9e07f8ee9e3'}
+```
diff --git a/voltha/adapters/openolt/openolt_data_model.py b/voltha/adapters/openolt/openolt_data_model.py
index 03db02a..8b30361 100644
--- a/voltha/adapters/openolt/openolt_data_model.py
+++ b/voltha/adapters/openolt/openolt_data_model.py
@@ -177,10 +177,23 @@
 
         if onu_device:
             self.log.debug("data_model onu update", intf_id=intf_id,
-                           onu_id=onu_id, serial_number=serial_number)
-            if onu_device.oper_status == OperStatus.ACTIVATING \
-                    or onu_device.oper_status == OperStatus.DISCOVERED:
+                           onu_id=onu_id, serial_number=serial_number,
+                           oper_state=onu_device.oper_status)
+            if onu_device.oper_status == OperStatus.UNKNOWN:
+                # olt reboot
+                self.log.debug("onu active or activating", intf_id=intf_id,
+                               onu_id=onu_id, serial_number=serial_number,
+                               oper_state=onu_device.oper_status)
+                onu_device.oper_status = OperStatus.DISCOVERED
+                onu_device.connect_status = ConnectStatus.REACHABLE
+                self.adapter_agent.update_device(onu_device)
+            else:
+                # onu activating
+                self.log.debug("onu active or activating", intf_id=intf_id,
+                               onu_id=onu_id, serial_number=serial_number,
+                               oper_state=onu_device.oper_status)
                 raise ValueError
+            return
 
         self.log.debug("data_model onu create", intf_id=intf_id,
                        onu_id=onu_id, serial_number=serial_number)