@ArchDevil This is possible, as long as it is done correctly. See this FAQ document for more information: General questions about Ethernet Backhaul feature on your Deco

@ZZLOW If you are getting 100Mbps from Main Deco, your Satellite #2 shouldn't get more than 25-30 if you can daisy chain it. Which means, not different from what you have. Buying more powerful Deco...

@ZZLOW If you happened to have M4 hardware V4, there should be configuration option to do that: How to select a preferred signal source on the Deco App If not, see this document: Is the Signal Source...

@Proterra The best WiFi speed I ever got from my M5 is 475Mbps. Realistically, expect around 400Mbps from Main Deco M5 and any Satellite Deco M5 with Ethernet backhaul, about half of that on...

@Headcoat Turn off WiFi network in ISP router, use Deco mesh WiFi network.

@WiCreekPaddler My recommendation would be to swap Office Deco M5 with Antenna Deco M4R. If this is hardware issue with specific M5 unit, the problem will go away.