WiFi Recovery USB Problems

[xA_A_Ron]

Hello.

So i have six Wifi APs, three NLS-1304-25 and three AC-1304. One of my AC-1304s is constantly offline and when it is online it provides slower than desired speeds. All of my APs are hardwired to a managed gigabit switch. I have tried everything on the outside of device to fix this, New wire, connect wirelessly, hard factory default reset, etc. 
so ive moved to the inside and ive been trying to reflash the firmware with a recovery USB. i made the USB with onHUB addon, i bought the usb-c hub... ive gone as reflashing ALL of my APs to prove to myself that it is not me going crazy, something is wrong with this particular AP. 
When i attempt to flash this device, i get to the point where the light is flashing orange, insert the recovery USB, and then nothing... it just keeps flashing orange. The recovery process on the other five devices was painless, but this one is becoming a headache.... and im about to send it to wifi heaven. 

Any feedback, suggestions, comments or psychiatric help appreciated. 

[MichaelP]

Hello @xA_A_Ron 

I'm afraid I can't help with the USB flashing, but I did want to comment on one thing I saw in your report above: you're using a managed Ethernet switch. This likely has loop detection enabled, which means it's running the Spanning Tree Protocol, which Google/Nest WiFi also use to support wired backhaul. To make this work, you will need to at least disable loop detection on that switch, and possibly enabled BPDU flooding, if the switch supports that. Also, just to double-check, you have a primary/router Google WiFi unit connected to your internet service through its WAN (globe) port, and its LAN (<->) port is connected to your switch, then every other secondary Google WiFi unit is connected to this switched network. Connecting all of them in parallel to the same outer network will not work.

[xA_A_Ron]

Stone Temple Pilots are definitely disabled, no STP on the switch or loop detection, just about everything is disabled by default. #1 Fixed Point Wireless ISP In on WAN, Out to switch Port1 on LAN. #2-6 in In from switch Port2-6 on LAN.
Ive now gone as far as opening it up, putting it in to Dev Mode (flashing purple) with the internal momentary switch. It goes through all the processes as it is supposed to, but when it reboots, it does not READ from usb.  bought usb drive with indicator led to verify.  Additionally i bought another used 3 pack of AC-1304 from offerup, replaced #3 and added #7 & #8, everything is working fine, but I still dont have an answer to the initial problem... so Ill keep at it, my dog house could use an AP too.