ATT workflow with Sercomm ST-01 GPON

When doing the ATT workflow with Sercomm ST-01 upon Subscriber delete/add or pon port disable/enable or onu disable/enable procedure the ONUS becomes stuck not accepting OMCI messages anymore.

critical situation is here:
ONU-Log:
81 18 48 0a 01 0c 01 03 10 00 01 03 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 28 f7 a8 e5 50
81 18 28 0a 01 0c 01 03 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 28 87 9e 49 aa
root@sercomm:~#
…

There should be more messages received from Voltha.
See omci hex dump:
000000 81 18 48 0a 01 0c 01 03 10 00 01 03 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 28
000000 81 18 28 0a 01 0c 01 03 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 28 87 9e 49 aa
000000 81 19 46 0a 00 54 10 c1 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 28
000000 81 19 46 0a 00 54 10 c1 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 28
000000 81 19 46 0a 00 54 10 c1 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 28
000000 81 1a 46 0a 01 0a 01 01 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 28
…
So message with TID 0x8119 is not received anymore on ONU.
But it is still visible in the OltAdapter:

{"level":"debug","ts":"2021-07-22T15:11:38.785Z","caller":"core/device_handler.go:1130","msg":"sent-omci-msg","instanceId":"open-olt-voltha-adapter-openolt-68bf49858b-82gfl","op-id":"287a5ba3d634961f","op-name":"openflow-flow-add","task-id":"40b49e93239852f6","task-name":"kafka-inter-adapter-rpc-OMCI_REQUEST","onu-id":1,"omciTransactionID":33049,"omciMsg":"8119460a005410c1000000000000000000000000000000000000000000000000000000000000000000000028","intf-id":0}

The issue of the ONU becoming "stuck" does not appear always on a particular ME, in our different iteration we have seen this issue hit on different ME and different Operation (For Ex: Create operation of MAC Bridge port config)

on the onu we see
<4>send failed -146
<4>send failed -146

a hard or soft reboot of the ONU does bring it back to life.