I made the mistake of updating the firmware in my X55 system yesterday, and now performance has gotten really weird.   Most of my devices (I have a lot) seem to be connecting ok, but my primary machines, an Apple MacBook Air M2 and a iPad (9th generation) are showing horrible performance.

My network bandwidth into the house is nominally 1.2Gbps.    Before the update, my MacBook would generally get 800+ Mbps, and the iPad would get 400 Mbps or so.   Now they're both getting around 50-100 kbps.   Yes, that's Kilobits per second.   Connections are unreliable; sometimes they fail to connect, sometimes they drop, etc.  I've been unable to connect to a mail server via it's external name from inside the network.   I've rebooted both devices, and that didn't help.   I've waited over 12 hours in case it was some sort of DHCP issue, but that didn't help.

One weird thing is that if I switch them to the Guest network, their performance is near normal, showing ~550 Mbps on the MacBook, and 300+ on the iPad.   Switching back to the main network causes the performance to drop off again.   So it's clearly not my ISP.    I've run the "network optimization" step, but that had no visible effect.

Other devices on the network are showing reasonable performance, it seems to be mainly these two that are screwed up.   My iPhone 12, for instance, gets ~400Mbps over the WiFi.

The satellite Deco's have shown some weird behavior.    Usually they're showing a solid green LED, but occassiionally they'll go flashing Red for a bit, then back to green.

Is there a way to rollback to a previous firmware version?   Or some hidden way to get more diagnostics from the app?

I'm about ready to sell this, and never come back to TP-Link.   This is not the first problem I've had with these devices (previously there were LED issues, but that's a separate thing).