Is 200Mbps your ISP speed? If a device loses it connection every hour, could a lease time be involved? Is there anything else in your environment that repeats every hour?
And it doesn't seem to be some other environmental issue, as the affected MBP and affected media bridge experience their hourly outages at different times, for example, the media bridge losing connection at 3 minutes past the hour, and the MBP at 27 minutes past the hour.
I agree, it's super strange! There are no malfunctioning Windows clients, so no insight to be had there.
I reconfigured my old RT-AC3200 as a media bridge temporarily so I could remove the RT-AC88U mesh node (by factory-resetting all the ASUS devices), in case the mesh configuration was the cause. It didn't seem to help. The purpose of the bridge (where I'd like the mesh node) was to supply wired connectivity to devices in my home office, but I could observe the hourly connection outages with or without any devices connected to the bridge; it didn't matter if it had wired clients on it or not.
Last weekend, a relative helped me install CAT6 cable between rooms so I can use wired backhaul between nodes, instead of wireless. Yesterday, I factory-reset the ASUS devices again, and am trying AiMesh again with the AXE11000 and AC88U (the AC3200 is not presently in use). So far, so good.
I have omitted static DHCP assignments and IPv6 from my configuration this time, as well. Perhaps one of these is somehow leading to the problems.
I also recall having used the WiFi Radar previously to try to get some info on channel availability in my neighborhood. It is conceivable some bug with the WiFi Radar (obviously it is extremely buggy; I don't recommend trying it) could've been involved.
I plan to leave things in this configuration for at least a week to see how things go. I can survive without native IPv6 for a while.
InSSIDer works well to see those networks in your area. https://www.metageek.com/support/downloads/