CBR 750 with xfinity

I'm on xfinity gig service and wanted to remove the xfinity xb7 modem because of a huge amount of devices that aren't able to connect. I bought the Cbr 750 Orbi modem/router/satellite and installed it. Initially I had my normal 1200-1400 mbps speed. In the last two days my speed dropped to around 600 and is not improving. I called xfinity, they say good signal on their end. Netgear says that 1 downstream channel is not locked and three upstream channels are not locked and that this is my problem? I'm not super knowledgeable on this. Both Netgear and xfinity are blaming the other of course. Just looking for ideas where to turn to fix this. If it can't be resolved I will have to go to some different hardware. These speeds won't work for me. Thanks so much!