go626201Mikrotik section:
On your HEX, can you run ping plotter and see if you still get packet lost on the router? If it didn't, your rb5009 is most definitely broken.
Mikrotik switch chip firmware do have bug, run supout and send it to Mikrotik.
But if your new ONU report error on Eth1 and Eth2 but absolutely zero error on other port, then it is mostly hardware failure as they are all connected to the same SoC, just using different lane and physical circuit on the PCB.
Do you still get ping spike with the HEX + new ONU?
Skyworth section:
Can screenshot me some of the Add option and relevant screen you tried?
But given the bugs that TM is having with their ONR, I think you better just reset the ONU and setup again, if you have the password and VOIP pin.
Example: The D-Link ONR cannot do port forwarding until firmware v2.0.6. It is crazy such simple function is broken for so long.
EDIT:
Just request for RMA. If they let you do it then you immediately rule out router problem.
From very early on I got a sus on it because you have that unusual packet loss in ping plotter which I cannot reproduce no matter how hard I try.
My ipv6 with my pc have some issue with hEX,so now cant ping with ipv6 on my pc.
for RMA,i not sure Subtel got or not.
I bought it for 2-3years already. Not sure can repair or not...