When you changed out a switch, meaning you had an external switch connected between the router and your wired devices? Did you directly connect the wired devices to the router, by passing the switch?
When you were testing, was streaming and moving large files all going on at the same time or separately?
I would recommend testing another DIR series router, either same model or different to see if the problem appears. Find a store with a return and refund policy. I recommend also testing all this out while the routers is not connected to the ISP modem.
I would phone contact DLink support so they get visibility on this. You might go back to v1.02 and confirm that the router doesn't hang with wire devices directly connected. If you can confirm it doesn't hang, then thats another item to mention to DLink support. Go to Level 2 or higher. This is something that needs higher attention.
Maybe someone can review your router settings with you using Link>
teamviewer if your interested. Its safe and secure.
Keep us posted.