I'm at wits end with 870

Thank you for taking the time to run these tests.  The 870 product is different than previous generations of Orbi systems.  Earlier systems used three sets of radios:

1. 2.4G radio for user devices
2. 5G radio for user devices
3. separate 5G radio for communication between router and satellites.

The 870 Technical Specifications describe it as using the 5G and 6G radios for both user devices and to communicate between router and satellites.

https://www.downloads.netgear.com/files/GDC/RBE871/RBE871_TS.pdf

Frustration with which Orbi unit a particular device chooses has been a factor since the first Orbi was released in 2016.  There is a suspicion that some devices "stop looking" once they connect to a specific WiFi access point.  This generally seems to be typical of devices which are not mobile.  They seem to be affected by Orbi system restarts in which the router begins broadcasting WiFi before the satellites.  Restarting the device after the Orbi system is fully operational often gets the device connected to a more desirable access point.

With Laptops being mobile, one would expect that the Thinkpad would notice when the connection to WiFi begins to suffer and automatically switch to a "better signal".  What you are observing might indicate that the Thinkpad made a 6GHz connection to one Orbi unit.  6GHz suffers more from distance and building materials than other frequencies, so if the Thinkpad does not automatically switch to a closer access point, that might explain the horrible performance you are seeing ..... until the WiFi is restarted deliberately.

It might be useful to test that hypothesis directly.  i.e. set up close to one satellite and perform a Speed Test.  Notice which access point Attached Devices shows the Thinkpad connected to.  Then move to the other satellite and test the speed there.  Wait several minutes to see if Attached Devices (or Device Manager on the app) shows the Thinkpad still connected to the original satellite.  (Those displays take quite some time to update.  My old Orbi will show my smartphone connected to the garage unit at 2.4G for quite some time after I enter the house and sit 4 feet from the router.)