Try using the lowest resolution video in your quest 3 as a test.
Is the router really hot when the network shuts down?
Make sure you have MIMO enabled on the router.
You mentioned setting a static IP, have you tried it?
Do you know if there has been a firmware update recently. ISP's can do that remotely.
Do you experience something similar when downloading one of the high resolution videos?
If at all possible, try streaming from a device in your home to the quest 3 as a test.
Also, is it a modem and a router separately, or a modem router in one?
This one might sound strange, but can you stream longer right after the router resets? Could be a memory leak, bad cleanup, a lot of partial packets saturating the memory... (of the router that is. Not your headset.)