Hi Bert,
Thank you for the follow up. I think I finally find the problem. It seems these pods did not get IPv4 address but instead previously only getting IPv6 address for some reason.
After I did the following, the lagging problem no longer there.
1. have pods connected via ethernet cable
2. restart modern
3. these pods are assigned with IPv4 addresses instead of the previous IPv6
The reason I noticed this is for some reason my phone was assigned with two IPv6 and one IPv4 address under the same WIFI SSID. So maybe the pods were too far away from the modern and was configured to work as independent AP instead. I am not sure how these pods work since there is no management UI to check the status.
For Velop, I can explicit set the working mode of wifi to bridging so it cannot perform DHCP service itself. The DHCP request simply relay back to Ziggo Smart modern, thus the setup is clear to me. If something is wrong with DHCP then it must be modern. But these pods seem able to do DHCP on their own so they are not in bridging mode but rather router mode.
Now the lagging problem is gone and pods are assigned properly with IPv4 addresses. However, I decide nevertheless to move back to Linksys Velop system since these pods are very difficult to debug without any management UI or possibility to perform manual configuration. I cannot even see which working mode is the pod set to.
Again thank you for the hlep. I think the problem can be closed.
Best Regards
Kuan Yan