RBR 50 - Slow speed on desktop only

Since only the desktops are having the problem, and if you have taken the advice about setting Orbi in AP mode since your modem / router cannot be bridged (by the way you may want to check with your ISP if Xfinity to see if you can get a device that can be bridged if you want to use Orbi as your primary router. They may do this since your unit is one of the older ones), I suspect there is something with your computer settings, if using Windows 10. Perhaps in a conflict of DNS. In the Orbi AP mode you should have your Technicolor controlling DNS this and it is most likely set for ISP providing. Unfortunately, the DNS cannot be changed in this model. So the assumption here is that after putting Orbi in AP mode you should have resolved the problem, but if not then you need to insure your computers are using the ISP provided DNS server, rather than another set up in them. This site may be helpful in checking that: https://www.windowscentral.com/how-change-your-pcs-dns-settings-windows-10