Thanks for contacting support, and providing the details of your setup, I’d be happy to take a look at the issue you are facing here. There are a few possibilities of what could be going wrong here but my initial suggestion would be to set up some firewall exceptions in your Router. You’ll want to forward:
UDP port 9003
TCP ports 9100-9200
You can read of a user with an issue similar to yours that was resolved by forwarding those ports:
Some users have also mentioned that enabling ‘Flow Control’ on their managed switches improve performance. I see that your Unifi Switch 8 is a managed switch and if it has the ability for ‘flow control’ I would suggest you enable it. You can read more about flow control and how it has solved people’s issue in these threads:
Please let me know if any of my suggestions help here but if they don’t, we can take a deeper look into what’s happening here.