Downgrade back to a Superhub 4

We got upgraded - both to a Hub 5 and both our Tivo 6 boxes to the 360s'

I know I am stuck with the 360's, but recently our Hub 5 has been constantly getting to a point where it is working, but I am seeing speeds of less than 1Mbps on a wired connection.  Really want to go back to the old Hub 4 as that was pretty rock solid - anyone managed to do that ?

I know the hubs are dire at anything sensible for home networking so are in modem mode and I run all my routing elsewhere.

When I get this problem, rebooting the superhub fixes it - nothing is showing as a problem in my router (running dd-wrt) or if I swap out for another running stock firmware.

I have read about people resetting the Superhub 5 which I have done and it was better for a whole whopping day.

No idea when it may do this slow down - can be any time of day or night. Not good with more streaming happening of an evening or those of us working during the day