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Make sure you turn off "smart setup" on the Homehub.
See link how to do that.
Some devices have a problem with the Homehub dual band having the same SSid (name). You should try splitting them.
Which hub are using. Can you post stats
Another possibility if you're using a smarthub is to turn Authoritative DHCP off (Advanced>My Network >IPv4 configuration).
Maybe its just my hub or devices but I've found that Authoritative DHCP can cause contention between the hub and the device