you tagged this in the wrong section as it's against the streaming devices that NOW once used to make and sell.
Try an ethernet connection.
Otherwise call the broadband team using the number from the below link.
I have a 3 floor house and use this: https://uk.pcmag.com/wi-fi-mesh-networking-systems/129007/amazon-eero-pro-6
Zero buffering and we have roku, appletv, skyq mini devices running everywhere - with a 1gb broadband connection, i get these speeds minimum 550mbps speed.