Turn the modem off, probably for at least 15 minutes. But before you do it check the modem status page first
http://192.168.100.1/ and look what downstream channel you are on. Then turn it off 15+ minutes and turn it back on again, give it a minute or so to boot and connect and then check if you on a new channel.
On overlay you locked to only 1 upstream channel tho, so can only change the downstream not the upstream. This new channel I am on is still is all over the place during today but this morning between midnight and 6am was a lot faster than my other channel.